INTERNATIONAL LABOUR OFFIGE

STUDIES AND REPORTS
Series N (Statistics) No. 14

METHODS OF COMPILING
STATISTICS OF COAL-MINING
ACCIDENTS

GENEVA
1929
Published in the United Kingdom
For the INTERNATIONAL LABOUR OFFICE (LEAGUE OF NATIONS)

By P. S. KING & SON, Ltd.
Orchard House, 14 Great Smith Street, Westminster, London, S. W. 1

CONTENTS
Pagre
INTRODUCTION

1

CHAPTER

I. — Casualties and Accidents
Casualties
Accidents

CHAPTER

II. — The Demarcation of Industrial Risk in Coal Mining 10
Coal-Mining Risk
10
The Risk Groups
13

CHAPTER

III. — The Measurement of Accident Risk
Frequency Rates
Severity Rates
The Exposure to Risk
Rates per Average Number of Workers
Rates per Number of Manshifts (Days) or Full-Time
Workers
Rates per Number of Hours Worked
Tonnage Rates and Rates per Aggregate Wages Paid.

CHAPTER

IV. — Classification by Causes

V. — An International Comparison of Coal-Mining
Accident
General Rates
Comparison by Causes
Rates by Causes
Percentages by Causes

5
5
8

17
17
21
23
24
26
28
34
37

CHAPTER

49
49
57
58
61

Notes on the Statistics of Coal-Mining Accidents in
Different Countries
65

APPENDIX.

INTRODUCTION

The methods of compiling statistics of industrial accidents
were discussed in a report of the International Labour Office
submitted in 1923 to the International Conference of Labour
Statisticians x, which adopted a series of resolutions thereon.
The subject, however, is so vast that a general study could
not treat all aspects exhaustively. The Office, therefore, has
continued its investigations in this direction and has studied
separately the industrial accident risk of certain branches of
industry.
In this Report statistics of coal-mining accidents are analysed
from the point of view of the methods of compilation. In
most coal-mining countries special mining statistics exist in
addition to the general insurance or compensation statistics,
and these only will be considered here. The main reason for
the compilation of special statistics is probably the particularly
high risk of accident in coal mining, which is closely connected
with the fact that unforeseen events which may involve the
lives of several persons are of special importance and frequency.
Such events, which constitute disturbances in the regular
operation of the mine, are to a large extent attributable to
the fact that the work is carried on underground. Falls of
ground, escapes of gas, and explosions of coal dust are events not
entirely within human control. Their injurious consequences,
however, frequently might be prevented.
On the other hand, disturbances of operation caused by
improper working, carelessness of the workers or fault of management are apt to be particularly frequent and easily result in
serious injury owing to the fact that work is often carried on
in the dark and on narrow underground roads. Access to
the mine by the shaft also involves particular dangers.
1

Methods of Compiling Statistics of Industrial Accidents.
and Reports, Series N, No. 3. Geneva, 1923.

Studies

— 2 —
Finally, apart from these disturbing events, the risk of injury
in any work carried on underground may be enhanced by
the special conditions of the :nine and the dampness of the
atmosphere.
In compensation statistics, the case of injury is the only
practical unit of the statistics, as the compensation paid for
the injury is the point of interest for the insurance institution.
Special statistics, however, attach interest mainly to the safety
point of view, and therefore also to the disturbing events
causing injury to persons. Actually a new unit is thus
introduced which does not appear in insurance statistics : the
" accident " as distinct from the case of injury, the term
" accident " referring to the event causing the injury, whilst
the case of injury refers to the person injured.
The term " accident ", which in insurance statistics can
only convey one meaning, viz. the case of injury, thus assumes
a different and often ambiguous meaning in special statistics.
Accident, on the one hand, and case of injury, which is termed
here "casualty" in accordance with the terminology employed
in British railway statistics, on the other, are easily distinguishable when a disturbing event interfering with the regular
working of the mine occurs, as, for instance, an explosion of
coal dust or a fall of ground. In many cases, however, it is
impossible to distinguish the material event from the casualty.
A haulage man, for instance, is crushed by falling from a tub.
In this case " accident " and " casualty " constitute in fact
one single case in a statistical sense. Nevertheless, even in
these cases the event is frequently recorded separately, i.e.
the case is recorded twice, once as an event usually termed
" accident ", and once under the heading " person injured ".
It is probable that this recording of the event resulting in
injury, irrespective of whether it is a disturbance of operation
or only a personal event, has led to ambiguity in the terminology
of coal-mining accident statistics. The inconsistency in the
terminology is still greater if special accident statistics for coal
mining, shipping and railways are considered, in all of which
the event is registered as a separate statistical unit.
In Great Britain, the term " accident " in coal-mining
statistics is applied vaguely in a general sense, while the term
" separate accident " refers to the disturbance of operation or
to any other unforeseen event causing injury to persons; the
cases of injury are classified under the headings " deaths

— 3 —
and injuries " or " persons killed and injured ". The term
" accident rates " is nevertheless applied to rates of cases
of injury x.
In the United States of America, " accident " generally
indicates either the disturbing or the personal event. In
coal-mining statistics, an accident is an event causing or resulting
in personal injury, the consequences being designated as
" fatality " and " non-fatal injury " 2. In Belgium and France,
" accident " is an event involving injury to persons. The
cases of injury are found under the headings " blessés " or
" tués " or " victimes ". The term " Unfall " in German
coal-mining statistics relates to the personal case of injury,
while " Unglücksfall " is reserved for the injurious event 3.
It would appear that, according to the predominant terminology, the term "accident" (Unglücksfall, accident) might best
be confined to the event resulting in injury, while the term
" casualty " (found in British and American railway statistics)

could with advantage be accepted as the term designating the
case of injury. In the course of this Report " accident " and
" casualty " are taken in this sense.

1
In British railway statistics, an accident is an event causing either
in jury or material damage, sometimes even an event likely to have
caused loss of life or injury ; the case of injury is termed " casualty ",
whereas in shipping statistics the term " casualty " designates,
on2 the contrary, the disturbing event involving the vessel.
In railway statistics, an accident is an event resulting either in
injury to persons or damage to railway property, while the " casualty "
is 3the case of injury.
In railway statistics, however, " Unfall " is the event resulting in
injury or damage, while the consequences are indicated under the
headings " Tötungen und Verletzungen ".

CHAPTER I
CASUALTIES AND ACCIDENTS
Casualties are reported under workmen's compensation legislation primarily for financial purposes. In order, however, to
study safety in different industries and the prevention of
accidents, special information must be obtained additional
to that on casualties compensated.
For coal-mining statistics, such information is largely derived
from the reports under compensation laws and completed in
some countries by reports under special legislation or special
provisions in the compensation laws.
CASUALTIES

In compiling special statistics the data derived from reports
under compensation legislation are usually adapted to the purposes of such statistics. These may include casualties notified
but not compensated, their aim being the measurement of the
risk during the period of reporting.
German insurance statistics, for instance, include those
casualties for which compensation was paid for the first time
in the year of reporting 1. Coal-mining statistics, however,
include all casualties notifiable under the insurance law, that
is, all casualties disabling for more than three days.
In Great Britain, the compensation statistics include all cases
compensated for the first time in the year under review, but
also, and separately, cases in which compensation was continued
from the previous year. In the special coal-mining statistics
furnished according to the provisions of the Mining Acts,
only cases occurring in the current year are included.
A further difference may arise in regard to the number of
fatal casualties reported in the two sets of statistics. The
compensation statistics generally include fatal cases in which
compensation was paid to the dependants of the deceased or
1
Fatal casualties and casualties lasting more than thirteen weeks.
Casualties lasting less than thirteen weeks are compensated under
sickness insurance.

— 6 —
in which funeral and medical benefits were granted. As
" fatal ", are considered those cases in which the death is
attributed to the accident anc usually include cases from the
previous year in which they were non-fatal ; on the other
hand, particular rules on the definition of fatal casualties are
usually laid down in the compilation of special statistics K
In addition to these discrepancies between compensation
statistics and special statistics, the industrial classification of
the former does not always agree with the demarcation of the
industry in the latter.
German insurance statistics, for
instance, include all casualties reported by the mining trade
unions (Knappschaftsberufsgencssenschaften) in the Reich indiscriminately, while special statistics exist for coal mines in
Prussia. In Great Britain, Belgium, and various other countries,
compensation statistics cover accidents in all mines, while
special statistics distinguish coal mines from other mines.
Though the objects of the special statistics, however, are
evidently much the same in the different countries, the definition
of reportable casualties in these statistics differs widely from
country to country.
With regard to fatal casualties, an accident may not result
in instantaneous death but cause an injury leading to death
after a shorter or longer period of incapacity. Each country
decides how far death occurring after the accident shall still be
attributable to the accident.
In British coal-mining statistics, for instance, a fatal casualty
is one which leads to death up to the date of the annual report,
with the restriction that a casualty is no longer classified as
fatal if death occurs later than one year and one day after the
accident. In German and Dutch coal-mining statistics a
casualty ending in death before the completion of the annual
report is recorded as fatal. The definition is rather vague in
French statistics (death must occur immediately after the
accident or at most some months later). In the United States
no period between the accident and the death is fixed, but in
practice statistics include those casualties that had resulted
in death when the State Mine Inspector of each State furnished
his summary to the Bureau of Mines. In Belgium, death
1

For further discussion and illustration oí this point, ci. NIXON :
" On Some Principles of Accident Statistics ", International Labour
Review, Dec. 1928.

_

7 —

must occur within thirty days from the occurrence of the. event.
In Czechoslovakia a fatal casualty is one which causes instantaneous death or leads to death, no limit being fixed for the
period which may elapse between the accident and death.
It will thus be seen that fatal casualties are not, strictly
speaking, comparable from country to country or even as between different statistics of the same country. Three methods
are applied for compiling fatal casualty statistics.
The first method reports as fatal all casualties which lead to
death up to the issue of the annual report. According to
another method, the period which may elapse between the
accident and death in order to render death accidental is limited.
A third method adds to the limitation of this period the
indication of a final date after which the fatal issue is no longer
considered for the special statistics.
While the limiting of the period elapsing between accident
and death is based on the consideration that the causal relation
between accident and death becomes doubtful if too long a
period elapses between the two, the other limit, the final date,
is necessitated by the fact that the issue of the casualties
occurring towards the end of the period of observation cannot
be awaited as the publication of the report would be greatly
delayed.
It is evident that casualties occurring in the year of observation may lead to death after months or even years. For
this reason insurance statistics in some countries are revised
after some years or published for longer periods. Such a revision can only be carried out by the insurance institution which
has control over the consequences of the casualties. It is a problem concerning accident statistics generally, and therefore cannot
be treated here. For special statistics, however, agreement
should be reached between the different countries on the
following points :
(1) Should the period which may elapse between the
occurrence of the accident and death be fixed ?
(2) What date is to be taken as the final date after
which a fatal issue is no longer to be taken into
consideration ?
It has been seen that the term " fatal casualty " is not a
uniform conception. The term " non-fatal casualty " evidently
is still less uniform. In Prussian statistics all casualties disabling

— 8 —
totally or partially for more than three days are reported since
1923, while prior to that date only fatal casualties were reported.
In Great Britain the limitation was seven days of incapacity
up to 1923 and three days since. In France all casualties
disabling for more than four days are published. In Belgian
statistics, casualties disabling permanently only are included.
In Holland all casualties disabling for more than three weeks and
in India all casualties enforcing absence from work for more
than twenty days or leading to serious injury as defined by law
are published. In Japan all non-fatal casualties are included but
classified as serious and slight, the latter including all injuries
disabling up to one week. In the United States of America
(federal statistics) non-fatal casualties are excluded altogether,
as the non-fatal casualties reported in the different States are
incomparable.
Some States report serious casualties only
(the definition of serious being even left to the discretion of the
reporting inspectors in some cases) and the limits with regard
to the severity of the reportable casualties vary. In Czechoslovakia, serious casualties are, on the one hand, those which
are serious in respect to the injury, that is, those which lead to
mutilation or permanent ill-health, and, on the other hand,
those serious only in respect to the duration of incapacity, the
latter including casualties disabling for more than nineteen days.
The effect of these differing limits of reportable casualties on
the comparability of frequency rates of non-fatal casualties will
be seen in the international comparison of coal-mining casualties.
It is evident that comparison of non-fatal casualties is almost
impossible so long as no agreement regarding their classification
by duration is reached. Classification by duration is not often
made in special statistics except in the case of classification
according to temporary and permanent incapacity. This
classification can only be based on insurance data and is a
general problem of accident statistics. It cannot therefore be
treated in this Report.
ACCIDENTS

Data on accidents as separate statistical units are usually
furnished along with the reports notifying the casualties.
Where the material event cannot be clearly distinguished from
the case of injury, accident and casualty are identical statistical
units. Some countries provide for a separate and special

— 9 —
notification of events involving injury to several persons or of
a nature which has or might have had serious consequences.
In Great Britain, for instance, certain accidents considered
serious have to be reported to the divisional inspector of mines
under the Mines Act, 1911. Accidents are thus reportable if
they result either in some specific kinds of injuries or are caused
by explosion of gas or dust, or by any explosive, by electricity or
by overwinding, and cause any personal injury whatever.
These accidents are published separately. Generally, all events
resulting in injury, disturbances of operation as well as other
injurious events, are registered separately as accidents. This
practice is adopted also in Indian, French and Belgian statistics.
An accident involving both fatal and non-fatal casualties would
be classified as fatal.
In the German statistics, accidents are altogether omitted
from the tables, notifiable mine disasters only being separately
mentioned in a descriptive way.

Dutch statistics are also

confined to casualties. The United States statistics report the
principal mine disasters ; first, those are reported which resulted
in a hundred or more deaths and secondly all accidents in which
five or more persons are killed. Special accident tables have
been published from time to time in which accidents are classified
according to the number of persons killed.
The number of accidents approximates very closely to that
of casualties where all the injurious events are registered as
" accidents ". It would appear, however, that interest attaches
only to those events which constitute disturbances of operation
and involve danger to one or several persons. If these events
only were registered as statistical units, distinct from the cases
of injury, the prevalence of disturbing events as well as their
importance with regard to casualties could be determined.

CHAPTER II
THE DEMARCATION OF INDUSTRIAL
IN COAL MINING

COAL-MINING

RISK

RISK

By the " coal-mining industry " is generally understood
the industry engaged in the extraction of coal. Accident
statistics aim at showing the industrial risk of coal miners, i.e.
the risk incurred during and in consequence of employment.
Accidents, therefore, sustained by the miner outside his
employment are not taken into account.
In order to show this risk, it is necessary to define it in such
a way as to demarcate it from other industrial risks on the one
hand and from non-industrial risks of the workers on the other
hand. The demarcation can either be based on the " enterprise ", or on the " premises ", or on the " worker ", viz. the
operation in which the worker is engaged.
(1) A " coal-mining enterprise " is a commercial or financial
unit and may cover processes of different technical character
combined for financial purposes, and therefore includes premises
annexed to the mines, as coke ovens, briquette works, etc., where
the coal raised is further treated and transformed, and even
iron foundries, power stations, and other works attached to
the mine in order to render the enterprise independent of raw
materials and other supplies.
The risk in these processes and premises is evidently very
different, as it depends largely on the technical process in which
the worker is engaged. The enterprise does not therefore seem
a suitable criterion of demarcation. For financial reasons, a
colliery company may possess many kinds of industrial works.
The criterion " enterprise " is, in fact, not applied in coalmining accident statistics.

— 11 —
(2) The operations, i.e. the processes in which the workers who
are victims of the accidents are engaged, is applied as criterion
in the Prussian and Indian statistics. In the former, all
casualties to mine workers (Belegschaft) and technical employees
in consequence of the mining process (infolge des Bergwerkbetriebs) during the shift are included. Thus the operation of
the worker and the causal relation between the casualty and the
process determine the inclusion of the casualty, while nonindustrial risks of the workers are excluded by the phrase "during
the shift " 1. Coke ovens, briquette works and other processes
for treating coal are considered as belonging to the mining
process. Similarly, coke making and the dressing of minerals
are covered by the Indian statistics. The statistics are then
grouped according to the minerals raised and prepared, viz.
coal, lignite, iron-ore, etc.
This method of demarcation, however, allows of different
applications ; and the inclusion of the ancillary processes of
dressing and treating coal extends the statistics to risks differing
essentially from the risks peculiar to the mine, i.e. the raising
of minerals underground.
(3) A third criterion of demarcation is the premises on which
the casualties happen. It is applied in most countries, e.g. Great
Britain, Belgium, France, and the Netherlands. According to
this criterion, all casualties happening to workers in and about
the mine are covered by the statistics. By this method casualties to the workers outside their employment are automatically
excluded. The exclusion of certain non-industrial " accidents "
which might happen in or about the mine, such as suicide,
homicide, and accidents due to ill-health, etc., is specially
provided for. The results of the second and third methods
are only slightly different with regard to the mine workers
properly so called. By a demarcation on the basis of the
premises, however, ancillary works, such as those above cited,
are excluded from the statistics — as in Great Britain, France,
Belgium, etc. On the other hand, not only technical employees.
but also clerical staff are covered, if not explicitly excluded as

1
It follows that casualties not connected with the mining process,
as those caused by lightning, suicide and homicide, casualties in consequence of unhealthy constitution and casualties on the way to and
from work and to other than mine workers, are excluded.

— 12 —
in Belgium, as they also work on the premises. Though clerical
staff have risks very different from those of the miners, they
form only a very small percentage of all mining workers, and, if
excluded, must be considered in another department of accident
statistics.
As coal-mining accidents are under consideration, it might
be argued that miners hewing or hauling other minerals than
coal in the same mine where mainly coal is raised are not " coal
miners ". The mining of such minerals, however, being carried
on under exactly the same conditions as that of the coal,
possibly by the same workers, will involve much the same
risks with the same causes.
To conclude, the third method of demarcation, by the premises,
would appear to be the most suitable one for coal-mining
accident statistics.
The term " coal " however, may refer to several kinds of
coal, such as bituminous, anthracite and lignite, for which the
technical process differs. The extraction of lignite does not
necessitate the sinking of shafts, and is therefore not liable to
the same risks as pit-coal mining. Bituminous and anthracite
coal mining may also entail different risks owing to the, natural
conditions under which they are raised.
The following tables show the risks attaching to anthracite,
bituminous and lignite mining.

PENNSYLVANIA : FATALITIES P E R 1 , 0 0 0 3 0 0 - D A Y

Bituminous
Year

1920
1921
1922
1923
1924
1925
1

WORKERS1

Anthracite

Underground
and surface

Underground

Underground
and surface

Underground

3.01
2.98
4.51
2.91
3.43
2.95

3.35
3.18
4.87
3.14
3.71
3.26

3.74
3.80
3.81
3.62
3.39
4.12

4.55
4.84
4.60
4.38
4.05
4.80

U.S. DEPABTMEKT OF COMMERCE, BUREAU OP MIKES : Coal Mine Fatalities in the:

United States, 192«. Bulletin 283, pp. 90 et aeq.

— 13 —

FATAL CASUALTY RATE

I N COAL MINING AND LIGNITE MINING
IN PRUSSIA

Year

1911
1912
1913
1920
1921
1922
1923
1924.
1

1

Pit-coal raining:
fatal casualties
per 1,000 workers

Lignite mining :
fatal casualties
per 1,000 workers

2.01
2.54
2.48
2.31
2.00
2.05
1.60
2.21

1.69
1.72
1.48
1.59
1.36
1.35
1.37
1.46

MINISTEBIUM FÜR HANDEL UND GEWEBBE, PBEÜSSEN : Zeitschrift für Berg-, Hütten-

und Salinenmeten im preussischen Staate. Berlin.

Lignite mining shows a considerably lower risk than pit-coal
mining, and bituminous coal mining a lower one than anthracite
mining. The latter difference, however, might be partly due
to the different classes of labour employed in the two coalfields : more immigrant and non-union labour being engaged in
anthracite, and more national and union labour in bituminous,
coalfields. Figures, therefore, should be published separately
for the different branches of coal mining.
T H E RISK GROUPS

A coal mine contains two distinct parts : underground workings and surface workings. Underground work has risks
peculiar to mining both with regard to the high incidence and
the causes of the casualties, which are largely disturbing
events easily involving several injuries. A distinction between
underground and surface risks is therefore fundamental.
There is another feature peculiar to the mine premises which
calls for attention : the shaft. The shaft is the way between
underground and surface through which all underground workers
and the coal must pass. As the shaft is usually, in European
mines, a vertical passage requiring special mechanical haulage,
accidents may happen in the shaft though the miners do not
work there ; and these accidents are apt to be serious, since
the breaking of ropes or chains, overwinding and even personal
events, as falls, are more dangerous in the shaft than elsewhere
below ground.

— 14 —
For these reasons the shafts are in some statistics considered
as separate premises of the mine, like underground and surface.
In other statistics, however, shaft accidents are considered as
a separate group of causes only. This is due to the fact that
for the calculation of rates there is no " shaft exposure "
which could be separately calculated, there being no " shaft
workers " as there are surface and underground workers.
A separate assessment of underground and surface risks,
however, is not sufficient, as these risks are unevenly distributed
between the different occupations, underground and surface
respectively.
Underground hewers may be most exposed to falls of ground,
while haulage men are most exposed to risk of haulage. The
following table for anthracite coal mining in Pennsylvania
illustrates the risk distribution of underground workers in those
mines. However, it is not necessarily representative of risk
distribution in other mines.

NUMBER KILLED P E R 1 , 0 0 0 WORKERS UNDERGROUND

Tears

1900-1913
1

Mine
Fire
foremen bosses
and as- and assistants sistants

2.98

3.86

Miners

6..00

Miners' Drivers
labourand
ers
runners

4.29

3.35

1

Door
boys,
etc.

AU
others

3.86

2.06

XL S. DEPARTMENT OF THE INTEBIOB, BUBKAC OP MINES : Coal Mine Fatalities in the

United States, 1870-1914, p. 95. Washington, 1916.

By far the greatest risk is found for miners properly speaking
(hewers and hewers' labourers), while the risks are low in the
cases of foremen and assistants and other underground workers
not directly employed in the getting of coal.
The occupations of surface workers are also very varied, as
besides the workers hauling, sorting and washing coal, skilled
workers are employed, such as enginemen, plumbers, and
sawyers, whose work and risks are similar to those in other
industries.
Technical employees, mainly entrusted with management
and surveying, may be working underground or on the surface.
Their accidents should be classified as underground or surface
accordingly.

— 15 —
A classification of accidents into underground and surface is
made in all coal-mining statistics. Classifications by occupations, however, are not, to our knowledge, given except in the
Pennsylvanian statistics, in the reports of the miners' insurance
funds, and in the English occupational mortality statistics \
In speaking of "underground" and "surface", however, one
may mean either the premises on which the accidents or casualties happen or the workers to which they happen. Underground
workers may have accidents whilst on the surface and surface
workers may be injured whilst temporarily assisting in some
work underground. In the British report for 1925, we find,
for instance, that the number of " persons injured underground " and " persons injured on the surface " in the table
of causes was 162,687 and 14,660 respectively, whilst in the
classification by nature and duration of injury the number of
" underground workers " injured was 163,253 and of " surface
workers " injured 14,094 ; t h e difference is due to a certain

number of underground workers being injured on the surface
and vice versa. In the first case, the classification of casualties
was made according to the premises, because the causes depend
on the premises ; in the second case, the classification was
made by the workers' occupations, probably because the
consequences of the injuries were known for each person only.
It is evident that statistics on the risk of underground work
and its causes should contain all accidents happening underground. The premises appear therefore to be the most suitable
criterion of classification.
It is otherwise, however, with regard to occupations. Most
workers have their regular occupation, no matter where they
happen to perform their job. A classification by occupations
only aims at showing the occupational risk of each occupation,
as distinct from the industrial risk of the whole industry,
i.e. of the premises. The classification by occupations must
nevertheless group occupations according to underground and
surface, as a technical worker and a repair or haulage man
usually employed in underground work cannot be grouped
together with the same kind of worker mainly employed in
surface work, their risks being too divergent. The occupational
1
Accidents in the new occupational mortality report for 1921-1923
comprise non-industrial casualties. Moreover, the " exposed to risk "
contains also retired workers.

— 16 —
classification of casualties by underground and surface will,
however, not entirely coincide with the classification by underground and surface premises.
As the terminology for coal-mining workers varies greatly
in different coalfields and countries, a uniform detailed international classification by occupations would be difficult. The
following summary classification, however, might be attempted :
Underground workers :
(a) hewers and assistants ;
(b) haulage men ;
(c) repair workers ;
(d) foremen, deputies, overmen, etc. ;
(e) other workers*
Surface workers:
(a) colliery weighmen ;
(b) coal washers ;
(c) coal pickers (coal cleaners, etc.) ;
(d) banksmen ;
(e) other haulage men, dirt tip men, etc. ;
(/) craftsmen (plumbers, enginemen, etc.) ;
(g) technical employees ;
(h) other surface workers.
Clerical worke.rs.

The tabulation and classification of casualties and accidents,
however, even if these are classified according to duration, does
not in itself furnish a comparison of the risks. By the " risk " ismeant the incidence of casualties as compared with the exposure,
and the measurement of this risk and of exposure offers special
problems in coal mining.

CHAPTER III
THE MEASUREMENT OF ACCIDENT RISK
The number of casualties alone does not give any information
as to the comparative risk incurred by the workers in different
countries or at different dates, as it necessarily depends to a
large extent on the number of workers engaged in the industry
and the amount of labour performed. The risk can only be
measured by relating the number of casualties and their consequences to the units of exposure to risk. The calculation of
rates, however, is a general problem of accident statistics and
we can only touch on some special aspects in this Report.
As both the number and the importance of casualties differ, it is
essential to measure both the frequency of the cases and their
severity. The severity rate is calculated by relating the time
lost to the exposure. The calculation of frequency and severity
rates offers certain difficulties as the rates are affected by
non-occupational factors, whose effects should be eliminated if
we desire to compare the industrial risks.
FREQUENCY RATES

Frequency rates should be independent of factors which may
be unequally distributed in the areas or industries concerned.
The main non-industrial factor affecting frequency rates is
age. There are circumstances which suggest that workers
may not be equally liable to accidents at every age ; new workers
entering mining, not being fully acquainted with the risks, are
likely to be less liable after they have adapted themselves to
their surroundings and learnt how to avoid dangers. The
reason is, of course, not their age but their inexperience ; it is
related to the age factor as the greatest number of new workers
are young workers.
As national coal-mining statistics do not generally publish
age-rates x, an instance is given from Heymann and Freudenberg's Morbidität und Mortalität der Bergleute im Ruhrgebiet
(Morbidity and Mortality of Ruhr Miners), and some data
1
The Report was already in the press when the British report for
1927 appeared, which contains a classification of fatal and non-fatal
casualties by age-groups and total casualty rates by age-groups.
The groups are as follows : under 16 years, 16 and under 18 years,
18 and under 20 years, 20 years and over.

_

18 —

F R E Q U E N C Y O F CASUALTIES BY AGE GROUPS
I N T H E RUHR COAL DISTRICT

1

Fatal and Non-Fatal Casualties per 1,000 Miners
Age

Up to 20
20-30
30-40
40-50
Over 50
Total

1907

1908

1909

1910

1911

1912

1913

19U

237.1
201.7
162.5
168.9
75.6

236.8
188.1
149.8
156.3
65.7

237.5
187.8
145.8
152.6
68.7

236.9
190.0
155.9
164.8
75.1

236.5
190.1
162.4
172.9
85.7

243.5
186.8
173.4
183.3
89.3

266.4
188.8
164.9
192.1
90.3

249.8
201.5
177.9
215.2
99.9

177.5 166.5 165.5 171.5 178.8 178.7 183.7 194.0

Age

1915

1916

1917

1918

Up to 20
20-30
30-40
40-50
Over 50

229.0
179.1
180.3
201.8
103.4

230.4
173.5
179.6
211.7
116.4

206.6
197.0
213.9
192.8
96.6

200.5
239.7
261.8
220.9
113.5

Total

1919

1920

1921

1922

183.9 180.7 190.7
112.6 116.3 100.8
114.5 86.7 81.8
144.9 111.8 104.8
107.0 95.1 89.7

—

185.7 188.5 187.7 211.8 133.4 120.2 113.7 102.0

Deaths by Accidents per 1,000 Miners
Age

1907

1908

1909

1910

1911

1912

1913

1914
i

Up to 20
20-30
30-40
40-50
Over 50

1.8
2.0
1.5
2.2
1.0

2.3
2.9
2.8
3.1
1.4

1.7
2.8
2.7
3.0
1.6

1.6
2.1
2.5
2.5
1.2

1.6
2.0
2.3
2.5
1.6

2.4
2.3
2.9
3.5
2.0

2.1
2.3
2.6
3.0
2.0

2.0
2.3
2.3
3.2
2.0

Total

1.8

2.7

2.5

2.1

2.1

2.7

2.4

2.4

Age

1915

1916

1917

1918

1919

1920

1921

1922

Up to 20
20-30
30-40
40-50
Over 50

2.5
2.4
2.8
4.3
2.5

2.3
2.2
3.6
5.4
3.1

2.4
2.7
4.6
5.3
3.8

1.6
2.3
4.4
4.2
2.7

1.7
1.5
2.2
3.7
3.0

1.5
1.7
1.8
2.6
2.8

1.5
1.4
1.5
2.4
2.3

1.4
1.5
1.7
2.5
2.2

Total

2.9

3.3

3.7

3.0

2.2

1.9

1.7

1.8

1
HEYMANN and FREUDENBERG : Morbidität und Mortalität der Bergleute im Ruhrgebiet,
pp. 170 et seq. Essen, 1925.

— 19 —
ENGLAND

AND WALES : FATAL CASUALTIES

IN COAL MINING

BY AGES, 1910, 1911, AND 1912 »
Age-group

15-19
20-24
25-34
35-44
45-54
55-64
65-74

75 and upwards

Workers in coal
raining *

Fatal
casualties

Fatal casualties
per 1,000 of population

429,486
396,222
677,898
512,451
316,455
170,814
65,982
13,185

466
449
797
663
457
279
56
2

1.08
1.13
1.17
1.29
1.44
1.63
0.85
0.15

2,582,493

3,169

1.23

' Mortality of Men in Certain Occupations. Supplement to the 75th Annual Report ol
the aRegistrar-General, Part IV, p. 25.
Census population of 1911 multiplied by three. Retired -workers are included.

from the English occupational mortality statistics of miners.
The British figures are taken from the occupational mortality
report for 1910-1912, as the new report for 1921-1923 does not
give the mining accidents separately, but classifies industrial
and non-industrial accidents of coal miners together.
According to the Ruhr statistics, which refer to fatal and
non-fatal industrial casualties of the occupied population, the
frequency of casualties generally (fatal and non-fatal) is highest
at youngest ages, that is, up to 20, and then drops down to
40, rising again between 40 and 50, and then decreasing very
considerably. The high frequency rate at youngest ages and
the subsequent decrease are probably due to the fact already
mentioned that young miners are not yet accustomed to their
work, nor acquainted with its dangers.
It may be added that, according to the English census
statistics for 1921, a large proportion of young men are engaged
in haulage work, the accident risk of which is very great. It
is of course difficult to decide how far high frequency rates at
younger ages may be due to the dangers of the haulage work
or how far the employment of young persons entering on mining
in haulage work raises the risk of this occupation.
The decrease of the total frequency rates towards higher ages
will, moreover, be accentuated by the elimination of unfit or
weaker workers who leave the occupation or die in consequence

— 20 —
of sickness or accidents. The rise between 40 and 50 in the
Ruhr is difficult to explain. The considerable decrease after
50 might be due to the fact that older men do not take on the
more dangerous jobs, or if so, only the specially experienced
and healthy workers. The age curve of the fatal casualty rate
does not show the same trend as the general casualty rate.
The rate on the whole rises with age up to 40 to 50 but drops
rather after that age, though the drop is much less marked in
post-war years. The rise may be due to the fact that older
men are more liable to disease and death generally and their
injuries therefore lead more frequently to death. The drop
after 50 can probably be explained in the same way as that of
the total frequency rate.
Occupational mortality statistics for England and Wales
show that fatal casualty rates of coal miners rise with age,
though much less so than the general death rate. The decline
in the case of the highest age groups is probably due to the
inclusion of retired workers in the statistics of exposure.
It may be concluded that age has an influence on accident
frequency. A classification of rates by ages is therefore desirable
in order to compare the risks at different ages. Moreover, the
different age incidence of casualties must be taken into account
in the calculation of total casualty rates (all ages) as the age
distribution of coal miners differs in the countries or areas
compared. Total frequency rates should therefore for international comparisons be standardised in regard to the age
distribution of the population under observation.
A problem similar to that of age would arise for sex were it
not that the proportion of women employed in coal mining
is negligible in most countries. Those employed, moreover,
are mainly engaged on the less dangerous jobs. In coal-mining
accident statistics, casualties, but not rates, are occasionally
published for the sexes separately.
There are other non-industrial factors besides age and sex
which may be differently distributed and affect casualty
rates, such as race and nationality of the workers. Certain
nationalities may be less careful and less skilled. It is evident
that fatal casualty rates will tend to be higher for those " races "
which are generally more liable to disease or have higher death
rates.
Apart from these " natural " factors, there are numerous
social and technical factors affecting casualty rates : the

— 21 —
standard of living of the industrial population, for instance,
which by influencing the health standard may weaken resistance
to the effects of casualties, and tend indirectly to affect rates.
The influence on accident frequency of labour conditions and
technical organisation, however, should not be eliminated in
the rates, as it is the aim of accident statistics to show the
differences in the risks due to different labour conditions and
organisation of production as well as those due to natural
conditions. Enquiries into these conditions are then no longer
a matter of statistics.
The industrial risk of accident, however, is not only or even
mainly expressed in the frequency of casualties. If frequency
rates were calculated for casualties classified by duration of
casualty, the comparison would be more fruitful, as the time
lost per case could be calculated, viz. the average duration of
the case. The measurement of risk by frequency rates, however,
can also be completed by the measurement of the risk by
severity rates relating the days lost directly to the exposure
to risk.
SEVERITY RATES

Severity rates, if correctly calculated, would in fact be a more
comparable measure of accident risk than frequency rates.
Their calculation, however, requires not only complete data,
but gives rise to certain difficulties owing to the fact that the
" time lost " by casualties is not always known.
Cases of injury may disable temporarily, permanently, or
lead to death. Casualties are usually reported for annual
periods and the exposure to risk is either the average number
of workers employed or the time worked during the year covered
by the statistics. The consequences of a casualty, however,
may last beyond the end of the year : a temporary case may
either last longer than one year or, as is more frequent, may
begin towards the end of one year and last into the next year.
The " time lost " in consequence of permanent disablement
and death may be taken as the remainder of the normal or
average working life or part thereof.
The total time lost as a result of temporary incapacity within
the year of accident occurrence can be related to the exposure of
that year as it represents the time actually lost as compared
with the time worked. The temporary severity rates, however,

— 22 —

would be inadequate as the time lost by cases lasting beyond
the end of the reporting period is not comprised, and this time
lost, escaping measurements, will differ in the areas or in the
States compared. This could be remedied to a certain extent
by computing in the rates of each period all time lost by casualties in that period, including time lost in consequence of casualties
which happened in the preceding year. The time lost by cases
of death and permanent disablement can only be estimated.
The problem of computing severity rates, however, is one of
accident statistics generally, since the data are mostly derived
from insurance statistics.
An American investigation into the severity of coal-mining
casualties in 1925 was based on the reports of fifty-nine coal
mines, furnished by the operating companies which participated
in the national safety competition of 1925 *. The reports
covered all " lost-time " casualties which occurred during
the year, that is, those which disabled an employee beyond
the day or shift on which the accident occurred. The mines
were situated in eleven States and covered each at least fifty
men underground. Each fatal case and case of permanent
total disability was weighted by 6,000 lost days according to
the scale of the International Association of Industrial Accident
Boards and Commissions 2. Permanent partial disability was
weighted according to the nature of the injury by using the
scale of the Board. Temporary injuries were weighted according
to the actual number of calendar days during which the employee
was incapacitated for work. It must be noted that in the
" 6,000-day weight ", the working days only are taken into
consideration (20 years = 6,000 days). The time lost by
temporary incapacity should consequently also include working
days only 3, which might be done as in Sweden by dividing the
days lost by 365 and multiplying the result by 300.
The average frequency rate was found to be 123 per million
hours of exposure, and the severity rate 10.214 days lost per
thousand hours of exposure. The two rates do not vary in
unison as the following tables show.
1
W. W. ADAMS : Accident Severity Rates for Certain Coal Mines.
Reports of Investigations, Department of Commerce, Bureau of Mines,
Serial No. 2783, Nov. 1926. (Typewritten report.)
2
Fatalities due to explosives were 'weighted by 12,000 days as required
by the rules governing the competition.
3
It is not clear whether this is the case here or not.

— 23 —
F R E Q U E N C Y AND SEVERITY RATES IN U N I T E D STATES MINES, 1 9 2 5
Size of mine
(number o E
employees)

Number
of
mines

Hours
worked

1-99
100-199
....
200 or m o r e . . .

6
17
36

828,312
4,960,099
23,329,150

State

Pennsylvania :
anthracite
bituminous
West Virginia
Utah

Total
Total
Accident Accident
number
number frequency
severity
of
of
rate
rate
accidents days lost

71
431
3,070

19,647
85.716 23.719
54,722 86.893 11.032
223,048 131.595 9.561

Hours
worked

Accident
frequencyrate per
million hours

Accident
severity
rate per
1,000 hours

4,890,295
3,684,991
3,946,989
5,706,078
1,327,463
1,622,929

94.677
50.746
47.631
322.638
109.984
133.093

8.871
10.772
9.114
10.453
15.022
19.528

It appears that the largest mines have the highest frequency
rate but the lowest severity rate, and the smallest mines the
lowest frequency rate and the highest severity rate. The
report comments upon this fact as follows :
It would thus appear that the larger companies are meeting with
reasonable success in keeping down their death rates, but that minor
injuries at their place still demand considerable attention it losses
caused by them are to be reduced.

It appears from the instance given that severity rates may
differ very considerably from frequency rates and that their
calculation would be of the greatest interest. Methods of
calculating severity rates, however, cannot be discussed here.
T H E E X P O S U R E TO R I S K

The worker is evidently exposed to risk of accident during
the time he spends at work, which, for the underground worker
means the time spent underground including the time for
descent and ascent. Time worked in mining differs in two
respects from manufacturing industry: (1)mines do not usually
or everywhere work continously throughout the year, but may
work a varying numbers of days ; and (2) the time worked by
the miners differs from mine to mine as well as individually.
The mine worked thus depends on various factors which may

— 24 —

vary from country to country such as : (a) the regular (agreed
or legally prescribed) hours of work, (b) the overtime or
supplementary hours worked, and short-time shifts as well as
winding time, and (c) the time lost by individual absences of
workers employed at the mine on account of sickness, accident»
holidays, or other reasons.
All these factors must be taken into account in assessing the
exposure to accident risk of coal miners. This, however, is
done in very varying degrees in the different statistics. It is
the aim of the following analysis to enquire to what extent
the rates calculated in the different countries allow for the
various time factors of exposure and to arrive at some conclusion as to the best method of assessing accident exposure in
coal mining.
In coal-mining accident statistics, the following casualty
rates are calculated :
(1) Rates per average number of workers (a) employed, and
(b) present ;
(2) Rates per number of manshifts worked, or rates per
man-days worked, or per full-time worker ;
(3) Rates per number of hours worked ;
(4) Rates per ton of coal raised ;
(5) Rates per aggregate wages paid.
Rates per Average Number of Workers
Rates per average number of workers are calculated by
different methods in the various coal-mining countries.
(a) The method employed in Great Britain and in the Netherlands, for instance, is to record the number of workers employed
at certain dates and to average these figures. Such an average,
however, will only be correct where the number of workers
employed at the mine on these dates is representative of the
daily number of workers employed. In the Dutch statistics,
the number of workers derived from fortnightly statements on
the wages books is divided by the periods of payment. In
Great Britain, quarterly statements of the numbers on the
colliery books are utilised.
(b) The method employed in Belgium, France, and India
is to add up the number of man-days actually worked or days

— 25 —

of presence and divide the sum by the number of days worked
by the mine. In Belgium and France the " jour de présence "
on days only when coal was wound are divided by the average
number of these days. In India all " daily attendances " are
divided by all days worked by the mine.
The so-called " average number of workers " thus found
is, however, only the average number of workers present on
each day the mine worked or coal was raised. It is not the
average number of workers employed ; it must be lower than
this average, as man-days lost owing to individual absences of
workers employed but not present on days the mine was open
are not taken into account. Nor does the average number
present, on the other hand, represent the time worked. The mandays actually worked, representing time worked, are divided
by the days on which coal was wound, and the differences in
time worked due to differences in the number of days on which
the mine was idle are thus eliminated 1 .
The correct method of calculating the average number
employed 2 would be to include in the total number of man-days
of the dividend not only those worked, but also those lost by
workers employed but absent owing to sickness, leave, etc.
This is done in Dutch statistics, where sick, injured and absent
workers are included in the " exposed to risk ". All man-days
worked and all man-days lost on all days when any work is
carried on in the mine should be included in the dividend, and
the sum divided by these days. Man-days lost should then
also comprise man-days lost on days when only few workers
worked, i.e. man-days lost owing to partial idleness of the
mine, but not those lost by complete idleness of the mine â.

1

For instance : in one mine, which works four days a week, 100, 105,
120, and 75 workers are respectively present. In another, six days
are worked by 100, 120, 80, 140, 60, and 100 respectively. In both
cases the average number present is 100, yet the man-days worked
are 400 and 600 respectively.
2
Rates of risk calculated by using this figure would be unsatisfactory, as workers who are sick or otherwise absent are not exposed
to risk.
3
Moreover, the average number of workers present must be relatively
smaller if man-days or manshifts on all days on which work was done
in the mine are divided by these days than if man-days worked on days
only when coal was wound are divided by this latter number, as fewer
workers will be working on the days when no coal was raised.

— 26 —

The " number of men employed " in the United States
coal-mining accident statistics is not based on any prescribed
method, but the calculation is left to the reporting operators.
According to the Geological Survey *, which prior to 1925
computed these figures, some of ;hese apply the method of
sampling by taking the average of each of the pay-rolls during
the year. The Geological Survey states that " this method
inflates statistics to the extent that the same employees appear
on the pay-rolls of two or more operations in the same period,
that is, duplication is introduced in proportion to the rapidity
of the labour turnover". Operators did not, however, include
pay-rolls for periods of strike or complete idleness of the
mine. The Geological Survey found that usually, however, the
figures reported were " not the average number of men actually
working at any time, nor the aggregate number of men who
had been working at the mine during the year, nor the absolute
average number of men on the pay-rolls, but rather the number
of men commonly dependent on the mine for employment " .
They represent the number ordinarily reporting for work when
the mine starts plus the absentees, that is, the men who have
been working recently and who will work again, but who for
one reason or another are not available.
Rates per Number of Manshifts (Days) or Full-Time Workers
Rates per average number of workers employed may actually
indicate variations of accident incidence in a coalfield or
differences between several coalfields of a country in relation
to employment and may be a suitable basis for insurance
calculations. Such rates, however, are not suitable for the
comparison of the risks peculiar to each mine or coalfield.
For international comparison these rates are misleading because
the time worked in one country may be longer than that worked
in another country. The same number of workers employed
is therefore exposed to risk during a longer time within the
same period in the one mine than in the other. We have seen
that the time worked by the employee in a mine may vary in
two respects : (a) according to the number of days worked by
each worker employed, which may differ (i) by the number of
1

1922,

U.S. GEOLOGICAL SURVEY : Mineral
pp. 494 et seq.

Resources of the United

States,

— 27 —

clays the mine was in operation during the period of observation,
and (ii) by the number of days on which the individual worker
was present ; and (b) according to the daily hours worked by
each employee present.
The mine may be idle during some days of the week or
during certain seasons of the year as well as in consequence of
strikes or lock-outs. Thus in the United States the number
of days worked varies enormously from State to State. In
1925, the number of days worked by the mines varied from
112 in Arkansas to 254 in Virginia 1.
These differences may be clue to natural conditions or to
commercial reasons. On the whole, as was stated by the
Geological Survey, which formerly computed these figures, the
larger mines work more steadily than the smaller mines. In
addition, the number of days lost by individual absences will differ.
A measure of accident risk taking account of this time factor
is the casualty rate related to the number of man-days or manshifts worked or to full-time workers based on man-days or
manshifts worked.
The number of normal manshifts, i.e. manshifts of the legally
prescribed or agreed number of hours, and of man-days are the
same where no overtime shifts are worked. Conditions, however, vary with regard to overtime. Where practically no
overtime is worked, as in Belgium and France, man-days and
manshifts are identical. In Great Britain, manshifts are calculated by including overtime and short-time reduced to shifts
of normal length.
A further difference must arise where, as in the United States,
the number of man-days is calculated by multiplying the number
of employees by the number of days the mines were in operation and coal was wound (tipple days). In order to compute
these " a c t i v e " days, the " o p e r a t o r " reporting is asked to
state the total number of full days the mine was in operation,
parts of days being reduced to full days 3.

1

Coal Mine Fatalities in the United States, 1926, op. cit., pp. 65-66.
The average number of days in each State is a weighted average.
Days worked by each mine are multiplied by the number of men employed at that mine and the sum of these products for all the mines in
the area considered is divided by the sum of the men employed. The
weighted average is considerably higher than the unweighted, owing to
the fact that large mines usually work more steadily than small mines.
2

— 28 —
The number of man-days thus calculated, which is divided
by 300 in order to arrive at full-time workers, is not necessarily
a correct measure of the man-days actually worked, as mandays lost by absence of underground workers on days when the
mine is working are usually included, whilst man-days worked
by underground or surface workers on days when no coal is
raised are excluded.
The so-called " full-time worker " of Prussian statistics was
for the years 1921 to 1925 found by adding up all regular
manshifts worked, short-time shifts being reduced to shifts of
normal length and the total sum divided by all ordinary working
days of the period. Overtime shifts were left out of account.
The measure thus obtained may diner according to the number
of general holidays in the respective coalfields.
The measure
was really calculated for the purposes of wages statistics and
meant to represent the full-day worker, for the calculation of
which overtime shifts are irrelevant, being worked on the same
days. For accident exposure, however, overtime represents
additional exposure. The calculation was in fact revised in
1926, overtime being included in the exposure.
Rates per Number of Hours Worked
Rates of casualties per manshift or man-days worked, or per
1,000 full-time workers calculated on man-days, take account
only of the number of days worked, but not of the number of
hours worked. The hours worked may differ (a) with regard
to the length of the normal shift worked, and (h) with regard
to the overtime worked in addition to the normal shift.
(a) Regular Hours of Work. — If the length of the shifts
varies, the time actually worked within the period of observation
may differ in two coalfields though the number of days worked
is the same. The difference between an eight- and a nine-hour
day, for instance, might amount to an addition of 12 per cent.
to the rate in the nine-hour coalfield. In Great Britain the
normal shift up to 1926 was of shorter duration than the German
normal shift.
The hours of work are fixed in the legislation or in collective
agreements according to different principles in different countries. The question is particularly complicated as regards
hours of work of underground workers. As a matter of fact»

— 29 —
the aggregate working time underground comprises not only
hours of effective work, but also time needed for travelling
from the shaft bottom to the place of work, breaks for meals,
as well as descent and ascent x .
It is evident that during the travelling time and breaks
underground the worker is exposed to a risk of accident. True,
this risk is different, if not smaller, than while at work; but
since the travelling time and breaks vary considerably not
only as between different individuals, but also from mine to
mine, it would be impracticable to establish a distinction
between the time of actual work at the face or other work,
and the rest of the time spent underground.
The case is somewhat different as regards the time needed
for descending to the shaft bottom and ascending to the surface,
i.e. " winding time ". Both during the descent and ascent the
worker is exposed to accident risk, and hence the total time
needed for them is to be included in the hours of exposure,
i.e. the total " hours of attendance ".
It is to be observed that the duration of a winding time
differs for each pit, a collective winding time being taken to
mean the average duration of the descent or ascent of all workers.
It depends not only on the depth of the shaft, but also on the
number of workers descending or ascending. In order to obtain
a correct idea of the length of the time during which the
underground workers are actually exposed to risk, it will be
necessary to calculate an average time of descent and ascent in
all cases where the regulation of the hours of work refers to
miners collectively, as is the general practice.
An examination of the conditions of work in mines shows
that an approximately exact average is obtained if, in calculating
the total hours of attendance, account is taken of half of the
total time needed for the descent and ascent of all cages, i.e.
of one winding time, as each worker must necessarily spend
underground the time it takes to lower those workers entering
after him and to raise those ascending before him.
Now, the legal or contractual hours may or may not include
the time of descent and ascent. In Germany, for instance,
1
For a detailed study of the method of determining hours of work
in coal mining, and of the actual differences found, see INTERNATIONAL
LABOUR OFFICE : Wages and Hours of Work in the Coal-Mining
Industry,
P a r t I, Chapter II, and P a r t II, Chapter I ; Studies and Reports, Series
D, No.18 ; Geneva, 1918.

— 31 —
was prior to 1926 not taken into account at all, though workers
are also exposed to risk during overtime. The same number of
full-time workers in two coalfields represented the same normal
time worked, but the overtime worked in the two coalfields
might differ and the actual time of exposure represented by a
full-time worker need not have been the same for the two
coalfields.
In those countries where practically no overtime is worked,
as in Belgium and France, the number of man-days worked
will be fairly representative of the time worked except for
differences in the winding times. Actual rates per hours
worked are calculated in the United States coal-mining accident
statistics. Fatal casualties are related to 2,000-hour workers.
As the actual number of hours worked by the miners is practically impossible to obtain, much coal being mined by contract
at a stated price per ton, rates are calculated which are " based
upon the number of hours the mines were in operation and
the employees were presumably at liberty to work, rather
than the number of hours the men actually worked " K The
piece-workers or tonnage men are not obliged to put in a
certain number of hours. Other workers engaged in maintenance, haulage and repair work are paid by the day and " their
hours conform more closely to the established working day of
the mine " 8. The hour-rate calculated in the United States
statistics for each State is obtained by multiplying the average
number of workers in mines working eight hours by eight, those
in mines working nine hours by nine, and so on. The products
added up give the number of hours worked per day by all employees in each State, which number is then multiplied by the
average number of days worked in the State per year, the
product giving the total hours worked per year. This figure,
or the average for the United States, is divided by 2,000 in
order to arrive at a 2,000-hour worker. This figure was chosen
because the working hours per year in the different States
ranged a few hours below and above 2,000, the average for the
United States being 1,909 (1903-1913).

1

Coal Mine Fatalities in the United Slates, 1920, op. cit., p. 45.
Mineral Resources of the United States, 1922, op. cit., P a r t II, 1925,
pp. 501 et seq.
2

30
one winding time is included in the eight-hour shift;. In Belgium, the normal shift comprises both winding times according
to the law, though the actual practice seems to vary in the
different districts. In France, both winding times are counted
within the eight-hour shift. In Great Britain, the legal hours
(seven prior to 1926, now eight) are counted from the last cage
down to the first cage up, that is, both winding times are
excluded from calculation of the legal hours of work. The
Netherlands mines count the normal shift as beginning with
the descent of the first worker and ending with the ascent of
the first worker, one winding time being thus included in the
shift. In Poland, according to the law the shift includes both
descent and ascent ; in Upper Silesia, however, only one winding
time is included, according to the collective agreement. In
Czechoslovakia, both winding times are comprised in the shift.
To arrive at a uniform determination of the average hours
of attendance as defined above, i.e. the total time spent underground, plus one winding time, the hours fixed by law or
agreement must be modified so as to exclude one winding
time when both descent and ascent are comprised, and to add
one winding time when only time spent underground is included
in these legal hours.
As regards surface workers, the determination of the length
of the shift does not present difficulties. The hours of exposure
are those of " real work " excluding breaks. The regulation
adopted in the different countries in this respect is practically
uniform.
(b) Overtime. — Not only the ordinary shift but also
the overtime shifts worked should be taken into account in
order to arrive at the time the workers were actually exposed
to risk. Overtime may also be worked in supplementary hours
added to normal shifts.
It is evident that for each overtime shift the same question
of the inclusion or exclusion of winding time arises. Overtime
shifts may be worked by part of the workers only, in which
case the descent or ascent will take less time than for the normal shifts worked by all workers. Such detailed data, however, will not be available. The best method, therefore, will be
to reduce overtime shifts to normal shifts and consider these
normal shifts as including one winding time each.
In the calculation of the German full-time worker, overtime

— 32 —
Some instances may be given showing the differences of rates
due to different methods of calculation.
UNITED STATES FATAL CASUALTIES IN 1923x
State

Kentucky
Ohio
West Virginia
1

Per 1,000 men
employee!

Per 1,000 300-day
workers

Per 1,000
2,000-hour
workers

2.96
1.70
2.00
2.11
2.38
2.06
3.70

3.83
3.23
4.37
4.19
4.78
2.91
6.56

2.95
2.69
3.63
3.43
3.96
2.41
5.43

Coal Mine Fatalities in the United States, 1924, op. cit., pp. 40 and 69. Washington, 1925.

The variations in the differences between the rates of the
several States due to the adoption of different methods of
calculation are striking, especially with regard to rates per
number of employees and rates per 300-day workers. If the
States are arranged according to accident frequency, the order
s as follows :
Gates per 1,000
men employed
Illinois
Indiana
Pennsylvania
Kentucky
Ohio
Alabama
W e s t Virginia

Bates per 1,000
300-day workers

Rates per 1,000
2,000-hour workers

Pennsylvania
Illinois
Alabama
Kentucky
Indiana
Ohio
West Virginia

Pennsylvania
Illinois
Alabama
Kentucky
Indiana
Ohio
W e s t Virginia

It appears from this comparison that the change is mainly
due to the difference in the number of days worked. The
following figures afford an explanation, showing the varying;
number of days worked in each State in 1923.
States

Ohio
W e s t Virginia

Men employed

Average days
worked
per year

30,035
99,714
35,408
60,811
54,555
194,981
117,300

232
158
136
152
150
213
169

Total hours
worked per year
60,409,784
126,184,014
38,563,616
75,198,352
65,671,800
333,880,908
159,915,743

— 33 —

To conclude, it appears that the best method of calculating
the time exposure to risk would be to take into account the
aggregate number of hours worked, separately for surface and
underground workers.
In order to arrive at a uniform computation of hours underground, the normal shift might be so calculated as to include
one winding time, as the first workers must necessarily descend
or ascend one winding time before the last workers.
If agreement were to be reached regarding standard international tables, each country could, for the purpose of filling
in these tables, then reduce its overtime shifts to shifts of
normal length. The total number of shifts spent underground
could then be converted into hours by taking the normal shift
to include one winding time. An English normal shift, for
instance, would have been seven hours plus one winding time
from 1919-1926, the Belgian shift eight hours minus one
winding time, and so on.

The hours worked in short-time

shifts, however, should be calculated separately and include
one winding time each. Moreover, supplementary hours should
be separately assessed. The table would read as follows :
Normal shifts
Country
or
district

Short-time shifts

Overtime shifts

Supple- Total
Number
mentary hours
reduced
to
Hours • hours worked
Number Hours ' Number Hours * Number
normal
shifts

• Each normal shift and each short time shift should include one winding time.

For surface workers, regular hours and overtime hours could
be calculated as in other industries.
Rates could then be calculated per million hours of work
or per standard manshifts of a certain length agreed upon
internationally. The hours might also be reduced to full-time
workers by dividing the hours actually worked by some figure,
say, 2,400 hours, assumed to make up a working year 1 .
1
The standard unit is somewhat arbitrary and would not be applicable
to all countries, e.g. the United States, where the working year is
exceptionally short.

— 34 —

Rates per hours worked are thus found to be the most
appropriate measure of the industrial risk of coal-mining labour.
In comparing the risks of underground and surface workers and
of the various occupations, rates must of course be calculated
for every risk group separately. The classification of the hours
of exposure by risk groups must evidently conform to the
classification of the casualties. For underground and surface
risk, casualties are most suitably classified by the premises.
The exposure consequently should relate to the hours worked
underground by all workers, on the one hand, and to the hours
worked above ground, on the other hand 1 . For the measurement
of occupational risk, however, casualties are classified according
to the ordinary occupation of the worker injured — the exposure
should, therefore, in this case, include all hours performed by
the workers of the occupation concerned, irrespective of whether
they were spent underground or on the surface.
All the rates so far discussed refer to labour exposure properly
so called. Most countries, however, publish in addition rates
in which the number of casualties is related to the tonnage
of coal raised.
Tonnage Rates and Rates per Aggregate Wages Paid
Tonnage rates are obviously not a suitable measure of the
accident risk of coal miners and are not meant as such. The risk
can only attach to the work and is only related to the tonnage
in so far as the amount of labour engaged in raising a ton of
coal represents a certain risk.
In the United States and Great Britain, for instance, fatal
casualty rates were as follows in 1925 :
Country

United States.
Great Britain.

Production
(short tons)

Men
employed

Kate per
1,000
workers

Rate per
1,000,000
tons

581,869,890
281,016,205

480,227
1,117,828

4.65
1.02

3.84
4.04

The rate in the United States is the rate per 1,000 300-day
workers. As the time worked by the mines in the United
1
As with casualties, there may be a difference in the relation of
underground exposure to surface exposure according tò whether the
unit of exposure is the underground or surface worker, or the day or
hour worked underground.

— 35 —
States is very irregular, the number of 300-day workers probably
corresponds more closely to the British calculation of average
number of workers employed than the average number of
workers. The average number of days worked in the year of
observation in Great Britain was 252, while in the United States
it was 192. Nevertheless, the higher rate in the United States
is partly accounted for by the different measure of exposure.
The production of short tons per 300-day worker was 1,212
short tons in the United States ; the risk per 1,000 workers was
4.65 ; per million tons it was therefore 4.65 divided by 1.212,
i.e. 3.84. The output per man in Great Britain was 251
short tons only, the rate per million tons is therefore 4.04, i.e.
higher than the American rate, whilst the rate per labour unit
was very much lower. If therefore the personal risk in the United
States is greater, the output per man is so much higher in the
United States that the accident rate per unit of coal raised is
lower than in Great Britain.
It might however be suggested that accidents may be related
to some units representing the cost of production in order to
compare the costs of accidents in different coalfields. The
tonnage rate might therefore serve to compare the incidence
of accidents per unit of production. A higher tonnage rate in
one of two coalfields compared would then suggest that the
accident compensation to be paid for each ton of coal raised
was a higher proportion of total costs in the former coalfield.
The output, however, is not a direct measure of the relative
cost of production, which depends on the wages paid and many
other factors besides, nor is the number or severity of accidents
a direct measure of the costs of compensation.
The tonnage rate, however, is of some economic interest as
it shows the loss of life and working capacity connected with
the raising of coal in different countries. A lower tonnage
rate in one of two countries compared shows that the same output does not involve so much loss of working capacity as in the
other country. Even if the risk of the worker is therefore
higher in that country the loss of working capacity paid for
each ton raised is lower.
Tonnage rates are calculated in the United States, Great
Britain, Germany, Canada, India, and other countries.
The tonnage to which the number and importance of accidents
is related can be either the coal raised including dirt, etc., or
the saleable coal, which includes the coal distributed to the

— 36 —

miners and the coal consumed by the mine. Finally, commercially disposable coal is defined as the coal after deduction of
the miners' coal and mine consumption. The measure usually
employed in calculating tonnage rates is the saleable coal.
This is the most appropriate measure as it represents the coal
which has value and realises an income in one form or another.
Another measure of " exposure to risk " is the aggregate
wages paid. Such rates are published in the report of the
Oregon Industrial Accident Commission. The number of
accidents and the days lost per 100,000 dollars of the pay-roll
are calculated. Wages paid, however, differ in various countries and coalfields and at different dates, and these differences
may have no relation whatever to the differences in time of
exposure or in the number of workers, but may be due to
differences in the rates of wages. The wages bill will change
with the changing of the time worked or the number of workers
employed, but also with a change in the rates of wages. The
wages bill would also change in consequence of changes in the
proportions of workers in the different occupations. The
rate of accidents per aggregate wages paid does therefore not
measure the risk of accident of the worker. It might, however,
serve as an indirect measure of the accident cost of production,
indicating the accident incidence compared with the wages
cost of production. In order to measure the cost of accidents
in relation to the costs of production, compensation cost rates
would be more appropriate.
To conclude, the rates per manhours worked have been
found to be the most suitable measure of the personal risk,
whilst tonnage rates may compare the accident risk connected
with the raising of a certain amount of coal.

CHAPTER IV
CLASSIFICATION BY CAUSES

A classification by causes is, in fact, an attempt to trace
the relation between the risk and the circumstances contributing
to bring about the casualty. The term " cause " is, however,
a somewhat vague notion ; strictly speaking it would refer to
the last preceding event resulting in injury, but in every case
there is a chain of " causes " leading finally up to the casualty.
In the case of a distinct disturbing material event, such as an
explosion, an eruption of water, a fall of ground, the causal
relation is clearly established. There still remains, however,
the question as to the cause of this event, which may be of
paramount interest for preventive purposes, e.g. a defective
safety lamp causing an explosion.
Where a personal event only occurs — such as being
crushed, or falling or stumbling — this event (the individual
circumstances) is usually the result of some hazardous occurrence
added to a regular process or act, by which coincidence the
danger inherent in the process or act becomes effective. In
these cases the event alone is not usually a sufficient indication
for preventive purposes, and the work or job during which it
happened should be added.
The events, whether disturbances of operation or personal
events, may be termed primary causes, while the circumstances
which cause the disturbances or the personal events may be
termed " secondary causes ". In addition, the process or
nature of the work in which the casualty happened and the
place where it happened may be of interest as indicating contributory circumstances.
In the existing classification casualties are grouped by the
four criteria :
(1)

Material event :
(a) disturbing event,
(i>) personal event ;
(2) Place;

— 38 —
(3) Process or nature of work ;
(4) Secondary circumstances.
Every classification by causes is, of course, based on a
distinction between underground and surface casualties. These
are always classified separately as the nature of the underground
and surface risks is entirely different.
The classification of underground casualties is based
wherever possible on the disturbing event : falls of ground,
explosion of gas or coal dust, mine fires, escape of water are
main groups to be found in all the more detailed classifications.
Where it is impossible to state such an event, we frequently
find the cases grouped by the nature of the work or the process :
" explosions " means casualties occurring during or by blasting and shooting operations, or while handling explosives;
the group " machinery " or " by mining tools and machinery "
refers to casualties caused by a mechanical process.
Special importance attaches to haulage casualties. In most
countries these casualties are grouped by the process of haulage,
but the local circumstances play a most important part.
Haulage accidents may happen on roads and gangways, on
inclines and slopes or in shafts, and their character and severity
depend to a considerable extent on the part of the mine where
they occur ; for most other casualties the place, though of
importance, does not indicate a different kind of risk.
Accordingly some countries group their haulage casualties
by place of occurrence.
A second problem arising in this connection is the special
risk connected with the shaft. With regard to the shaft, there
are different conceptions.
The shaft may be regarded (a) as a separate kind of premises,
like underground and surface ; or simply (ft) as a place underground where an accident may happen. Finally, (c) accidents
in the shaft may be considered from the point of view of the
process for which the shaft serves, the winding machinery and
haulage by or during which the accidents happen serving as
criterion of the classification.
A review may now be made of the classifications of the
United States, Prussia, and Great Britain, which may be
regarded as representative of the classifications in force.
Special reference is made to the methods of dealing with
shafts.

— 39 —
1. In the classification of the United States, the shafts
have been considered as separate parts of the mine. The group
" shaft accidents " , therefore, is added as a third main group
to the two groups " underground " and " surface " accidents
and is similary subdivided by "causes". Haulage casualties
occurring elsewhere below ground are considered as a causal
group of " underground accidents ". The classification reads
as follows :
Underground
(i)
Falls of roof (coal, rock, etc.) :
(a) at working face,
(ft) in room or chamber,
(c) on road, entry, or gangway,
(d) on slope.
(ii)
Falls of face or pillar coal :
(a) at working face,
(ft) on road, entry, or gangway.
(iii)
Mine cars and locomotives :
(a) switching and spragging,
(ft) coupling cars,
(c) falling from trips,
(d) run over by car or motor,
(<?) caught between car and rib,
(/) caught between car and roof while riding,
(g) runaway car or trip,
(ft) miscellaneous.
(iv)
Explosions of gas or coal dust :
(a) due to open light,
(ft) due to defective safety lamps,
(c) due to electric arc,
(d) due to shot,
(e) due to explosions of powder,
(/) miscellaneous.
(v)
Use of explosives :
(o) transportation,
(ft) charging,
(c) suffocation,
(d) drilling into old holes,
(e) striking in loose rock or coal,
(/) thawing,
(g) caps, detonators, etc.
(h) unguarded shots,
(/) returned too soon,
(/') premature shot,
(k) sparks from match, lamp, or candle,
(/) delayed blast,
(m) shot breaking through rib or pillar,
(n) miscellaneous.
• (vi)
Suffocation from mine gases.
(vii)
Electricity :
(a) direct contact with trolly wire,
(ft) bar or tool striking trolly wire,
(c) contact with mining machine,
(d) contact with machine feed wire,
(e) contact with haulage motor,
(/) miscellaneous.

— 40 —
(via)
(ix)
(x)
(xi)

(i)
(ii)
(iii)

(iv)

Animals.
Mining machines (other than vii, e).
Mine fires (burned, suffocated, etc.).
Other causes :
(a) fall of person,
(&) machinery (other than ix),
(c) rush of coal or gob,
(d) falling timber,
(e) suftocation in chutes,
(/) hand tools, axes, bars, etc.
(g) nails, splinters, etc.
(ft) miscellaneous.
Shaft
Falling down shafts or slopes.
Objects fallings down shafts or slopes.
Cage, skip, or bucket :
(a) runaway,
(b) riding with rock or coal,
(c) riding with timber or tools,
(d) struck by,
(e) miscellaneous.
Other causes :
(a) overwinding,
(ft) breaking of cables,
(c) miscellaneous.
Surface

(i)
(ii)
(iii)
(iv)
(v)
(vi)

Mine cars and mine locomotives.
Electricity.
Machinery.
Boiler explosions or bursting steam pipes.
Railway cars and locomotives.
Other causes :
(a) explosives,
(ft) fall of persons,
(c) falling objects (derricks, booms, etc.).
(d) suffocation in chute, bin, or culm,
(e) falls or slides of rock or coal,
(/) steam shovels,
(g) hand tools,
(ft) miscellaneous.

In this classification, the main groups of underground casualties refer to the disturbing event (falls of roof, etc., explosions,
mine fires, mine gases), where such an event occurred, or to the
process, e.g. processes connected with electricity, machinery,
animals, mine cars, explosives.
The subdivisions complete the main groups by being based
either on the place or local circumstances (at working face, on
road, etc.) ; the personal event (falling from trips, caught

— 41 —
between car and rib, run over, falls, etc.) ; the nature of the
work (switching, coupling, drilling, etc.) ; or, on the other
hand, a secondary cause of importance for preventive purposes,
which is frequently an act or a failure to act (open light, sparks
from match, unguarded shots, etc.).
In grouping shaft casualties, similar criteria are applied
as in the case of underground and surface accidents. Surface
casualties are mainly grouped by the nature of the work.
2. In the Prussian classification, more stress is laid on the
place where the casualty occurs.
Thus, the shaft is put on an equal footing with slopes, level
gangways, etc., and the grouping of casualties according to
these places is predominant. Also, haulage and winding
casualties are split up into three local groups : " main shafts ",
small blind shafts and slopes ", and " level gangways " ; which
groups, however, also contain certain casualties not due to
haulage. The subdivisions usually indicate the process during
or by which the accident happened.
The other main groups take the event as criterion, but are
to a large extent subdivided so as to indicate the place where
the accident occurred.
(i)

(ii)
(iii)

(iv)

(v)

Underground
Falls of stones :
(a) in main shafts,
(b) in small blind shafts and slopes,
(c) in level gangways,
(d) at working face,
By mining tools and mining machinery.
In main shafts :
(a) whilst ascending or descending (on ladders),
(b) on Fahrkunst (moving poles),
(c) haulage of persons by machinery (permitted),
(d) haulage of persons by machinery (not permitted),
(e) at winding service,
(/) working in or at the shaft,
(g) other causes.
In small blind shafts and slopes :
(a) falls of persons,
(b) haulage of persons by machinery (permitted),
(c) haulage of persons by machinery (not permitted),
(d) by winding gear,
(e) other causes.
In level gangways :
(a) whilst passing,
(b) mechanical transport of persons (permitted),
(c) mechanical transport of persons (not permitted),
(a) haulage by machinery,
(/) horse haulage,
(g) hand haulage,
(h) other causes.

— 42 —
(vi)
(vii)

(viii)

(ix)

(x)

At the working face.
By explosives :
(a) during storage or transport,
(b) whilst shooting or blasting,
(c) by explosive gases.
By gases and coal dust :
(a) explosions of fire-damp and coal-dust,
(b) suffocation by mine gases,
(c) by other natural gases.
By mine fires :
(a) fire in seams,
(b) fire in shaft or seat,
(c) fire in other parts of the mine.
Other causes :
(a) eruptions of water,
(b) machinery,
(c) other causes.

Surface
(i)
At the pit-mouth (hang-bank), including the shaft frame and
winding machinery (An der Hängebank einschl. Schachtgerüst und Fördermaschine).
(ii)
Whilst preparing coal.
(ih)
In briquette, coke or charcoal works, etc.
(iv)
Whilst hauling and loading :
(a) by railway cars and locomotives,
(i>) otherwise.
(v)
At boiler :
(a) by explosions,
(b) otherwise.
(vi)
By generating or transmitting power :
(a) by electrical current,
(b) by compressed air,
(c) otherwise.
(vii)
Other causes.
3. In the British classification shaft accidents are regarded
from the point of view of the process going on in the shaft, i.e.
the haulage and winding by machinery, etc. ; and " shaft
accidents " consequently constitute a main group of causes on
the same lines as " falls of ground " , " explosions of gases " ,
and " underground haulage " accidents. The method is not
always quite consistent in as far as certain shaft accidents not
connected with haulage and winding are included in the group,
the shaft being in these instances considered as a place.

(i)
(ii)

Underground
Explosions of fire-damp or coal-dust.
Falls of ground :
a) at the working face,
b) on roads while repairing or enlarging,
(c) on roads while otherwise working or passing,
(d) in shafts.

— 43 —
(iii)

Shaft accidents :
(a) overwinding,
(b) ropes or chains breaking,
(c) whilst descending or ascending by machinery,
(d) falling into shaft from surface,
(e) falling from part way down,
(/) things falling into shaft from surface,
(g) things falling from part way down,
(ft) other shaft accidents.

(iv)

Underground haulage accidents :
(a) ropes or chains breaking,
(i>) run over or crushed by trams or tubs :
(¡)
mechanical haulage,
(if) horse haulage,
(iii) hand haulage,
(iv) runaway trams or tubs,
(c) other haulage accidents.

(v)

Miscellaneous underground :
(a) by explosives,
(b) suffocation by natural gases,
(c) by underground fires,
(d) irruptions of water,
(e) electricity,
(/) by machinery,
(g) other accidents.
Surface

(i)
(ii)
(iii)

(iv)
(v)

By machinery.
Boiler explosions.
On railways, sidings or tramways :
(a) while engaged in moving wagons,
(¿>) while engaged in coupling or uncoupling wagons,
(c) run over while passing along or across railways or tramways,
(d) crushed between wagons and structures,
(e) in other ways.
Electricity.
Other accidents.

The fact that " falls of ground " in shafts are classified under
" falls of ground " and not under " shaft accidents " confirms
the view that the group " shaft " is meant to indicate not
mainly the place, but the kind of work or the process during
which the accident occurred. It is probably intended that
haulage accidents should contain accidents due to haulage and
not accidents occurring on haulage roads, and the group therefore
is meant in a causal and not in a local sense. Investigations
have shown that some confusion evidently arises from the
combined heading " cause or place of accident " . Some people
(classifying by place) regard a haulage accident as an accident
which happens on a haulage road, while others (classifying by

— 44 —
cause) regard an accident which is not due to any haulage
operation as not being a haulage accident, even though it occurs
on a haulage road. For haulage accidents no further indication
of the place is given. The two subdivisions, " ropes and chains
breaking " and " run over or crushed by trams or tubs ", are
not mutually quite exclusive x ; the one indicates the disturbing
event, whilst the other takes the personal event, i.e. the individual
circumstances, as criterion. " Ropes and chains breaking "
therefore may also cause someone to be run over or crushed by
tubs and trams. The second group, moreover, is subdivided by
the nature of the process. This subdivision of haulage accidents
might be considered unsatisfactory as the group " other haulage
accidents " contains approximately up to 50 per cent, of all
non-fatal haulage accidents.
In the Belgian classification the heading " shaft accidents "
does not coincide with the British group " shaft accidents ",
as blind shafts and working shafts (cheminées d'exploitation)
are included, and not only winding shafts, though the nature
of their risks is quite different from that of main shafts. The
distinction between the three is, however, made in the detailed
tables 2. On the other hand, haulage casualties other than in
these shafts are subdivided by the place where the casualty
happens, casualties on level roads and on inclined roads being
distinguished. These groups are then subdivided according
to the nature of the process.
As to casualties other than those due to haulage and shaft
accidents, both the British and the Belgian classifications
attempt to indicate to some extent the disturbing event or the
secondary cause — which may be a defect or an act or failure
to act — as well as the process during or in consequence of which
the casualty happened. Occasionally the place of the casualty
is given. The Belgian classification goes as far as to include a
fourth subdivision for certain kinds of casualties and gives a
detailed indication of the combined causes. Casualties due to
coal gas, for instance, are subdivided in the following way:
normal escape : (1) explosion and (2) suffocation ; (1) is

1
It is noted in the statistics that the group " run over or crushed
by trams or tubs " does not include accidents primarily due to ropes
and chains breaking.
2
Falls of ground occurring in these shafts are given in the shaft
groups and not under the heading " falls of ground ".

— 45 —
subdivided (a) by fuse, (b) by lamps, etc., and (c) by divers
causes ; group (b) is further subdivided by " open lamps "
and " defects " ; sudden irruptions : (1) explosions, (2) suffocation, struck by coal or stone, etc.
The differences in the classifications are thus considerable,
but agreement should not be impossible. A tentative classification might be proposed on the following lines. As shaft
accidents in almost all countries are considered as a special
group and the risk in the shaft is of a particular character,
distinguishing it from the risk on the haulage roads, the shaft
could, for the purpose of grouping the casualties, be considered
as a separate part of the underground premises. The shaft in
this sense should include only the main shafts, that is, winding
shafts and not blind shafts or slopes serving as entrances to
the mine or any other underground passage 1. The shaft
would therefore be the vertical entrance to the mine through
which coal and persons are wound. It does not seem advisable,
however, to classify shaft casualties quite apart from underground casualties and on the same footing, because shaft casualties
happen to all kinds of underground workers descending or
ascending the shaft or otherwise occupied near the shaft.
In calculating rates for shaft casualties, therefore, all work
performed underground is generally taken as exposure.
The main groups of casualties could be based on an indication
of the disturbing event or the process, while the subdivisions
could specify the further circumstances attending the casualty
by applying any of the other criteria most appropriate for the
purpose : either the individual circumstances (personal event),
the place, the nature of the work, or a secondary cause of
importance for preventive purposes.
It is of great importance to render the groups mutually
exclusive. Groups based on the personal event or individual
circumstances should not overlap with groups based on the
disturbing event, which may easily happen, as every disturbing
event also involves personal events.
The following tentative classification by causes might therefore be proposed :

1
The question whether very steep slopes serving as entrances to the
mine, and therefore subject to conditions similar to shafts, should be
reckoned as shafts might be left to the discretion of the Governments.

— 46 —
I. Shaft Accidents
Falls of ground, etc.
,
Falls of objects.
Falling down shaft :
(a) while working at shaft,
(b) from ladders, or while othsrwise ascending or descending
not by machinery,
(c) otherwise.
(iv)
Winding accidents :
(a) chains or ropes breaking,
(i>) overwinding,
(c) other accidents whilst descending or ascending by machi-1
nery.
(d) other winding accidents.
(v)
Struck by cage, bucket, etc.
(vi)
Other shaft accidents.
II. Other Underground Accidents
(i)
Falls of ground (coal, stone, etc.) :
(a) at the working face,
(b) on roads, slopes, gangways, etc.
(ii)
Explosions of gas and coal dust :
(a) fire-damp and coal dust,
'
(b) other gases.
.
(iii)
Suffocation by mine gases.
(iv)
Shooting and blasting accidents (" explosives ") :
'
(a) premature shot,
(b) delayed explosion,
(c) explosions during transport, handling or charging 1 :
(i)
from sparks of matches, lamps, etc.,
(ii) other causes,
(d) explosions of previously unexploded remnants,
(e) stones projected by shots,
(/) other causes.
(v)
Mine fires.
(vi)
Underground haulage :
(a) run over, crushed or otherwise injured by trams, tubs, etc.;
(i) mechanical haulage,
(ii) horse haulage,
(iii) hand haulage,
(vi) other haulage,
(&) injured by animals,
(c) falling, stumbling or slipping, during haulage operations,
(d) other haulage accidents.
(vii)
Mining machinery 2 and tools.
(via)
Electricity.
(ix)
Irruptions of water.
(x)
Miscellaneous :
.
(a) falls of persons,
(b) rushes of coal, gob, etc.,
(c) struck by objects
or striking against objects,
(d) machinery 3,
(e) other accidents.
1
Exclusive of premature shot, i.e. of the intended explosion happening too. soon.
:
•
3
Exclusive of accidents due to electricity.
.;• •
* Exclusive1 of accidents due to mining machinery.
•' ..
(i)
(ii)
(iii)

— 47 —

(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
(viii)

III. Surface
Surface haulage and transport accidents :
(a) run over, crushed or otherwise injured by trams, tubs, etc.,
(b) idem, by railway cars or engines, etc.,
(c) otherwise.
Machinery.
Boiler explosions, etc.
Electricity.
Irruptions of water.
Explosives.
Falls of persons.
Other surface accidents.
IV. Accidents to Clerical Workers
*

*

*

In calculating rates by causes, casualties of each group
underground should be related to the hours worked underground
by all workers or by the ¡group concerned * ; the same method
should be applied in the case of surface casualties.
The classification of aricidents by causes according to underground, shaft and surface accidents, however, does, not necessarily indicate to which group of workers the accident happened.
Haulage accidents, for instance, may happen to workers
engaged in haulage operations or to hewers or other workers
passing by the roads to the working face. Thus, the British
statistics of 1924 show that, of 262 fatal haulage accidents, 165
occurred among workers engaged in haulage operations, 44
to workers :walking to and from their work, and 53 in other
ways. Falls of ground are usually given separately for the
working face and for the roads, but falls of ground on a road
may also hit a worker walking to or from the working face.
Suffocation by mine gases or injuries by explosions may happen
to different classes of workers. It would therefore be of great
interest to group accidents by causes also according to the
occupation to which the injured worker belongs.
This classification would .differ from that according to
underground and surface workings in as far as surface workers
may have accidents underground and vice versa ; the groups
" accidents of underground occupations " and of " surface
occupations " would therefore not entirely correspond to the
two groups " underground " and " surface " accidents. By
classifying the casualties of each occupation by causes, each of
the two great groups would have to contain a heading, " surface "
1

See Chapter V, pp. 58 et seq.

48
accidents " and " underground accidents " respectively. The
casualties of each occupation by each cause would then be
related to all hours worked by the members of that occupation,
whether performed underground or on the surface. The following
classification of casualties by occupations and by causes might
complete the classification by parts of the mine and by causes,
and the statistics would indicate which groups of workers are
mainly exposed to certain kinds of accidents.
UNDERGROUND OCCUPATIONS

Hewers Haulage Repair Foremen, Other All underand as- men
deputies, workers ground
sistants
workers
etc.
workers

Causes
A. Underground :
(2) Falls of ground
(3) Explosions of gas and
(4) Suffocation by mine gases
(5) Shooting and blasting . .
(7) Underground h a u l a g e . . .
(8) Mining machinery a n d
(9) Electricity

•3.5P

o»
A. Surface :
Surface haulage and
Boiler explosions..
Electricity
Irruptions of water
Falls of persons . . .
Other surface acciB. Underground

i

li

Other
haulage
men,
etc.

fe>§
SE
-•?

OCCUPATIONS
Coal
pickers,
etc.

SURFACE

ss
GO

1I 4

CHAPTER V
AN INTERNATIONAL COMPARISON
OF COAL-MINING ACCIDENTS

GENERAL RATES

In view of the fact that the statistics of coal-mining accidents
in the several coal-produçing countries are fairly detailed,
an international comparison would seem feasible. Analysis,
however, has shown that such a comparison is greatly hampered
by differences in the methods of compilation and calculation.
A summary of the reasons which make comparison almost
impossible is given below.
It might seem at first sight that fatal casualty rates would be
readily comparable, as death is a unique and indisputable
event. Unfortunately, however, " death by accident " is not
so ; a fatal casualty is liable to different interpretations. Death
by accident is not always instantaneous ; it will therefore
depend on the legislative or other prescriptions to what extent
deaths occurring after the accident are still attributed to the
latter. In many cases the length of time elapsing between
accident and death is taken as criterion.
It has been seen that this question is solved in different
ways in the special statistics of the several countries, the
maximum period which may elapse between the occurrence of
the accident and death ensuing varying between thirty days in
Belgium and a year and a day in Great Britain.
As no data are available for coal-mining statistics for measuring the effects of such differences in methods on the resulting
figures, an example was taken from the United States railway
accidents statistics for 1924, where a difference of 11.3 per cent.
was found between the fatal casualties rate calculated on the
basis of casualties resulting in death within twenty-four hours
(0.69) and the rate including death up to the date of reporting
(0.78).
Even fatal casualties being not strictly comparable, it is not
surprising to find non-fatal casualties altogether incomparable.
On the one hand, the limitation of the period of incapacity which

— 50 —
must result from the casualty in order to make it reportable
in statistics differs from country to country, varying from more
than three days of incapacity to work in Great Britain and
Prussia, to permanent disability in Belgium. On the other
hand, casualties are in, most cases not classified by duration,
or, if so classified, no rates are calculated for the duration groups.
It is evident that rates calculated on such different bases
are really measures of totally different kinds of risks. If, for
instance, the total casualty rate (fatal and non-fatal) per thousand " workers present " in Belgium is found to be 1.37 (1925)
while the British total casualty rate per thousand 300-shift
workers is 191.7. the first rate indicates the risk of being
killed or permanently disabled, while the second rate is to
be the far greater risk of death or injury entailing incapacity to
work for more than three days. Fatal casualties being relatively
few in number, rates for non-fatal casualties are not likely
to differ much from total casualty rates if the former include
all casualties except those of very short duration.
The
difference is, however, considerable where the non-fatal group
only comprises permanently disabling casualties, as in Belgium.
Total casualty rates in Great Britain and in Prussia and nonfatal casualty rates in France may be considered fairly comparable. The inclusion of fatal casualties in the former countries will not affect the comparability to any considerable
extent. On the other hand, the non-fatal casualties include
in both countries casualties disabling for more than three days.
The minimum period of incapacity in France is five days.
Reference to these rates is made below.
Apart from differences in the definition of reportable casualties there are other sources of incomparability. Such a source
is to be found in differences in the field covered by the statistics :
this may differ in two respects : with regard to the premises
covered, and with regard to the categories of workers covered.
The condition that the casualty must be caused by mining
operations or by industrial operations connected with mining
coincides closely with the condition that the casualty must
have occurred on the premises of the mine. It can, however,
be modified with regard to the premises by the inclusion or
exclusion of certain kinds of workers employed on these premises : Prussian and Indian statistics, for instance, include
casualties to workers in ancillary works such as coke ovens and
briquette works, workers engaged in the dressing of coal, etc.,

— 51 —
which in most other countries are excluded from the statistics.
Casualty rates may be affected by these differences, as the risk
in ancillary works is likely to be lower than the risk in the mine
itself, and the inclusion of casualties in ancillary works among
the mine casualties and of the ancillary workers in the exposure to risk of mine workers is likely to lower the total rate. The
effect, however, will not be very considerable, as ancillary
workers are likely to be few in comparison with the total
number of mine workers. In Belgium, for instance, the number
of workers employed in ancillary works was approximately 4.9
per cent, of the number of workers in coal mining proper in
1926 (7,919 to 160,197) ». In the Ruhr district (Niederrheinisch-Westfälischer Bezirk), shifts worked by ancillary workers
in 1925 accounted for not quite 8 per cent, of shifts worked by
all workers in coal mining and ancillary works (7,924,071 to
118,005,809) \
As regards the mine itself, the scope may differ in respect
of the inclusion or exclusion of clerical workers ; they are
excluded in the American and Belgian statistics, and included
in most of the other statistics. The effect, however, of this
factor can only be slight, as clerical workers play a very small
part in coal mining. British statistics for 1925 show 1.7 per
cent, of all persons employed in coal mining to be clerks and
salaried persons (19,145 to 1,117,828). As such workers have
very few casualties, however, their inclusion in the statistics
will nevertheless slightly lower the rate.
The differences so far discussed however, are comparatively
slight. If the rates themselves are compared, it is found that
the main source of in comparability lies in the methods of
calculating the rates, that is, in the calculation of the exposure
to risk.
The data available with regard to the exposure to risk may
be summarised as follows :
United States of America
(1) Actual average number of employees : methods of computation
left to the reporting operators.
(2) 300-day workers found by multiplying the number of employees
by the number of days the mines wound coal and dividing
by 300.
1
Statistique des Industries extractives et métallurgiques en Belgique,
1926.
Tables II and IV (agglomérés et coke). Brussels, 1927.
2
The relation of the numbers of full-time workers is different, i.e.
about 6 per cent. (23,039 to 374,864), as the shifts include overtime
shifts, and more overtime was worked in ancillary works.

52
(3) 2,000-hour workers calculated by multiplying the number of
workers in each State by the standard hours of work at the
mines, and the products by the average number of days the
mines wound coal in each State and dividing by 2,000.
The number of man-hours worked is also utilised.
Great Britain
(1) Average number of workers employed during the year ascertained
by quarterly statements of thè numbers on the colliery books
and clerks and salaried persons.
(2) Manshifts worked including short-time shifts and overtime shifts
reduced to normal time.
Prussia
(1) Full-time workers and technical employees combined. Up to 1926
the former figure was found by dividing the sum of normal manshifts worked by the number of all ordinary working days ;
since 1926 overtime shifts reduced to normal shifts are included.
For the technical employees their average during the year is
taken.
Belgium
(1) Average number of workers present, calculated by dividing the
man-days worked on days when the mine wound coal by
these days.
(2) Man-days worked on all days the mine was open.
France
Average daily number of workers present found by dividing the
man-days worked by the days the mine worked.
Netherlands
Average number of employees found bjf dividing the total number of
workers ascertained fortnightly from the pay-sheets by the
periods of payment, including [sick, injured and absent workers.
India
Daily average number of persons employed, found by dividing the
aggregate number of daily attendances of persons permanently
and temporarily employed by the number of days worked by
the mine.

Rates per average number of workers — where only rates
per full-day workers are calculated, the latter have been compiled — are shown in the following table for fatal casualties,
underground and surface workers combined, for 1920 to 1926.
FATAL

CASUALTIES

PER

1,000

1920-1926

" WORKERS

Rates

Country
1920

1921

1922

2.90
3.78
0.88
1.13
0.97
2.31
0.98
1.06

2.42
4.20
0.87
0.89
0.94
2.00
1.35
1.18

2.35
4.90
0.95
0.93
0.82
2.05
1.13
1.01

1923

1924

1925

1926

2.98
4.65
1.02
0.92
1.18
2.70
1.07
1.33

3.32
4.50
1.08
0.99
1.03
2.30
1.00
1.06

United States
of America :
per average number
per 300-day workers
Great Britain

Netherlands

2 . 8 5 3.08
4.39 4.80
1.06 0.98
1.09 1.17
0.86 0.98
1.60 2 . 2 1
1.82 1.23
1.28 0 . 9 3

— 53 —
The great differences in these rates are largely due to differences in the number of days worked by the mine. This appears
at once from a comparison of the two rates in the United States.
The figures for 1922 will be taken as an example for the
following deductions. In 1922 the United States mines worked
an average of only 144 days, the ratio therefore of the two
rates — the rate per average number and per 300-day worker —
is 144 to 300, the second rate being 108 per cent, higher l.
Some idea of the comparative value of the rates based on
the average number of workers will be gained by comparing
the number of days worked by the mines in a few countries :
AVERAGE NUMBER OF DAYS WORKED BY T H E MINES IN 1 9 2 2

Prussia
United States

302
144

Great Britain
Belgium

262
295

It appears from the above figures that the rate per thousand
workers is relatively much too low in the United States as
compared with the other countries because the number of days
of exposure of these workers is much smaller than the number
of days of exposure of 1,000 workers in Great Britain, Prussia,
and Belgium. The British rate is somewhat too low as compared
with the Belgian rate. The Prussian rate is relatively too high
as compared with the British and American rates ; the 302 days
are ordinary working days, each full-time worker being
supposed to have worked this number of days 2.
It must, however, be kept in mind that the number of " days
worked by the mine " are not calculated on quite the same
methods in the different countries.
Comparison might seem more fruitful if the rates per manshifts
worked or per full-time worker were compared. It will appear
from these rates how far the rates per thousand workers are
modified by differences in the time worked. The following
fatal casualty rates are given in the statistics for 1922 :

1

For pre-war coal-mining accidents see also : DEPARTMENT OF THE
: Coal-Mining Statistics in the United
States and Foreign Countries, by F. W. HORTON, Bulletin No. 69 ;
Washington, 1913. In this study a re-calculation on a 300-day basis
was made for the United States, France, and Belgium.
2
The figure refers to the Dortmund district. The numbers of working
days in the other districts were as follows: Upper Silesia, 297; Lower
Silesia, 305 ; Left Rhine, 305 ; Aachen, 302.
INTERIOR, BUREAU OF MINES

— 54 —
• United States
Great Britain
Belgium
Prussia

4.90
0.39
0.305
2.045

per 1,000 300-day workers.
„ 100,000 manshifts worked.
„
„ 1,000 full-time workers.

In order to facilitate comparison, the British and Belgian
manshifts (days) are reduced to 300-shift or day workers. The
rates, however, are still not completely comparable because
the British shifts include overtime and short-time shifts reduced
to normal shifts, while the Prussian full-time worker represents
normal shifts or days. Moreover, the ordinary working days
constituting the divisor of the Prussian rate are not necessarily
300, but 302 in this particular case. The rate for Prussia has
been recalculated on the basis of 300 days. The number of
man-days in the United States may be overstated, as man-days
lost by individual absences on coal-winding days might be
included.
The rates per thousand 300-day workers would be as follows :
United States of America 4.90
Great Britain
1.17

Belgium
Prussia

0.915
2.031

In the United States the ratio of the full-time casualty rate
to the average worker casualty rate (4.90 : 2.35) corresponds to
that of the number of days (300 : 144). In Great Britain, the
rate per 1,000 average number employed and the rate per
1,000 300-day workers (0.95 : 1.17) do not bear exactly the
same relation to each other as the days worked (262) to the
300 days of the full-time workers. This is probably due to
a lower degree of accuracy in the ascertainment of the number
of workers employed than in that of the number of manshifts
worked. In later reports the two relations almost agree—for
instance, in 1925 1 .
It would be expected that the Belgian full-time worker rate
would be also higher than the average worker rate as the relation of the days is 300 to 295. It is, however, lower. This
result is due to the fact that the average number of workers
is calculated by taking into account the manshifts on coalwinding days only, whilst the full-time rate refers to all
manshifts worked, the full-time rate being lower because the
difference between all manshifts worked and^manshifts worked on
1
A slight difference will always remain, as the rates per 100,000
manshifts are calculated for mines exclusive of stratified ironstone mines
in Cleveland, Lincolnshire, and Northamptonshire, while these are included in the calculation of the rates per average number of workers
employed.

— 55 —
coal-winding days is greater than the difference between the days K
The rate per full-time workers based on the number of
days worked, however, takes no account, of differences in the
hours worked in the several countries. In considering the
hours worked it must be kept in mind that all observations
relating to winding time and shifts, etc., do not apply to surface
workers, the hours of whom may differ considerably from those
of underground workers. The estimates made below are therefore approximate only.
If the winding time is taken into account, the regular working hours at the time of observation (1922) were approximately
7 1 / 2 in Great Britain, 7 hours 50 minutes in Belgium, 8 hours in
Germany and 8 in most States of the Unites States, where,
however, nothing is known about the winding time.
In addition to these differences in regular hours, differences
in overtime worked would have to be taken into account.
If rates per hours worked, including overtime, were calculated,
the differences in the rates would be less as between Prussia
on the one hand and Great Britain and Belgium on the other,
and that for two reasons :
(1) The regular hours in 1922 were longer in Prussia
than in the two other countries.
(2) Considerable overtime is worked in Prussia, which
is not included in the number of manshifts as is done
in Great Britain. In Belgium overtime is not usually
worked.
In 1922, the total number of manshifts worked in Prussian
cpal mines was 198,078,758, the number of overtime shifts
was 14,407,687. Therefore, overtime worked was 7.8 per cent.
of the normal and short time worked.
Some idea of the change which would be effected in the rates
by taking into account the hours worked will be gained if rates
per thousand 2,400-hour workers are re-calculated on the
assumption of 8 hours plus 7.8 per cent, overtime (=approximately
8 hours 37 minutes) in Prussia, and 7 hours 50 minutes and
7 */2 hours in Belgium and Great Britain respectively. The
United States figures are re-calculated from the rate per
1,000 2,000-hour worker (4.04) 2.
1
All manshifts worked : 46,590,260 ; manshifts on coal-winding days :
45,113,970.
2
The calculations could of course be made more accurately by
taking the absolute figures as basis ; the above method, however, is
intended to bring out more clearly the theoretical aspect.

56 —

Fatal casualty rates per 1,000 2,400-hour workers would
have been approximately as follows ; the original rates per
average number of workers are given in brackets in order to
show the ensuing differences :
United States 4.848
Belgium
0.934

1
a

(2.350)
(0.930)

Great Britain 1.250 « (0.950)
Prussia
1.886 * (2.045)

The differences in the rates as between Great Britain, Prussia
and Belgium are thus considerably reduced, a part of the
excess of the Prussian rate being due to the methods applied
in calculating the exposure.
Rates ought really to be compared for underground and
surface workers separately. The above calculation was not made
for underground work alone because the rates per manshift
in Great Britain and the rate per 2,000-hour workers in the
United States are not calculated for underground and surface
workers separately. It will be seen from the comparison of
the underground and surface rates in the different countries
that the differences as between the countries of the total rates
are largely due to differences in the underground rates. This
may be due either actually to differences in risks or to the fact
that differences in the number of days worked by the mine
and in the hours worked are more considerable for underground
than surface workers, the comparability of the underground rates
being thus more impaired than the comparability of the surface
rates by differences of methods 3.
A rather interesting confirmation of the approximation which
would ensue between the rates of the different countries if
similar methods of calculation were applied may be seen in
the similarity of the total casualty rates of underground and
surface workers in Prussia and Great Britain. In both countries the minimum period of incapacity for a reportable casualty
1

The rate is slightly lower than the 300-day worker rate because
the hours taken into account in calculating the rate per 2,000-hour
worker are on an average slightly more than eight.
„ „ t „ ... .
1.17x2,400
0.915 x 2,400 x 60
D , .
2 Great B n t a m :
Belgmm :
7.5x300
470x300
2.031x2,400x60
PrUSSla :
517X300.
3
Moreover, underground rates may be affected by the methods of
allotting the units of exposure to underground and surface. In some
cases underground exposure relates to all underground workers, in
others to all time worked underground.

— 57 —
is three days. The Prussian rate refers to full-time workers,
the calculation of which is based on normal shifts worked exclusive of overtime; the British rate is re-calculated per 1,000
300-shift workers from the rate per 100,000 manshifts, and
includes overtime shifts reduced to shifts of normal length.
The rates are as follows :
Year

Prussia

Great Britain

1923
1924
1925
1926

65.06
176.00
199.70
215.91

201.9
188.7
191.7
201.9

The Prussian rate is even lower than the British rate in 1923
and 1924, and would be still more so if overtime and length
of shifts were taken into account 1 . It must, however, be kept
in mind that these rates are mainly determined by the non-fatal
risk, which may be actually relatively lower in Prussia than the
fatal risk.

COMPARISON B Y CAUSES

Comparison of the risk of coal miners in different countries
is thus found to be rendered almost impossible by the differences in the methods of compiling statistics. It might seem
somewhat more fruitful to compare the relative importance of
the different causes of accident risk underground (a) by means
of percentages, and (6) by comparison of the rates by causes
within each country.
Even such comparisons, however, are very much hampered
by the differences in the classifications by causes. Similar
headings do not always represent comparable groups. The
summary table " Shaft accidents " in Belgium for instance, for
which rates are calculated, covers main shafts and slopes, blind
shafts and working shafts, which groups are given separately
in the detailed tables only. The British and German groups refer
to main shafts and the United States group to shafts and slopes.
" Falls of ground " in some countries comprise all falls of
ground wherever they occur, while in other statistics falls of
ground in the shaft are included among shaft accidents.
1
The very low Prussian rate in 1923 may be due to curtailed production owing to the Ruhr occupation.

— 58 —
Haulage accidents in Belgium {circulation des ouvriers et
transport des produits) cover only casualties on level gangways
or slopes, but not those in blind shafts and working shafts, etc.
Rates byi Causes
As regards rates by causes, the in comparability is still greater
than in the case of comparison of general rates owing to
differences in classification. Also until recently rates for
casualties by causes in the United States statistics were
calculated per million hours of labour performed underground
and at the surface. They were therefore evidently much lower
than those in the other countries where rates by causes
underground are related to underground exposure only.
FATAL CASUALTIES D U E TO FALLS OF GROUND AND TO HAULAGE P E R
WORKERS EMPLOYED OR HOURS P E R F O R M E D UNDERGROUND *
United States

Tear
1920
1921
1922
1923
1924
1925
1926

G r e a t Britain
F a l l s of
ground

0.970
0.350
0.55 •
1.077
0358
0.55
1.123 ' ' 0.422 ' 0 5 9
0.60
1.038
0.367
0.62'
1.053
• 0.351
0.61
0.372
1.111
0.68

F a l l s of
ground

Haulage

Belgium

Prussia

France

Haulage

F a l l s of
ground

Haulage

F a l l s of
ground

Haulage

F a l l s of
ground

Haulage

0.24'
0.25
0.23
032
0.27
0.29
0.32

1.05
0.85
0.95
0.70
i:20
1.30
1.39

1.01
0.81
0.S6
0.60
0.90
0.90
0.93

0.50'
0.47
0.38
0.50
Ó.44
0.44
0.46

0,23
0.20
019
0.27
0.23
0.26
0.26

059
0.43
0.46
0.51
0.58
0.49
0.58

0.13
0.1,7
0 08
016
0.28
0.22
0.28

!

1
The measures of exposure in the different countries are as follows : United
States : million man-hours underground : Great Britain : 1,000 workers employed
underground ; Prussia : 1,000 full-time workers ; Belgium:. 1,000 workers present;
France : 1,000 workers present.

But rates by causes per underground exposure, even if the'
methods applied were the same, are only very approximate
measures of the various kinds of risks : t h e various groups of

underground workers are not equally exposed to the different
kinds of risk ; haulage casualties, for instance, happen mainly
to haulage workers, falls of ground to a large extent to hewers
at the working face 1.
1 I n G r e a t B r i t a i n c a s u a l t i e s b y falls of g r o u n d i n 1926 w e r e d i s t r i b u t e d "
a s follows : '
•
'
Place
Killed
Injured
At working face
820
23,952
On roads while repairing and enlarging . . . .
64
3,240
„
„
„
otherwise working or passing. •
45
2,667
In shafts.
1
20
Total. .
33Ö
29379 '

— 59 —
By referring casualties by causes to all work performed
underground, differences in the classification of the man-hours
according to the parts of the mine where they are worked are
not taken into account. These differences are considerable.
In Great Britain, for instance, the estimated number of manshifts
actually worked at the coal face in 1925 was 108,679,000,
as against 108,270,000 elsewhere below ground, or more than
50 per cent, of all manshifts worked underground. In Belgium,
the number of man-days worked by hewers and getters in 1925
was 6,496,605, as compared with a total number of man-days
worked underground of 33,094,070, or round about 20 per cent.
of the total number of man-days worked underground. In
Prussia (1924) the ratio of hewers to all underground workers
was 15.7 to 69.3 in Upper Silesia, 32.7 to 68.2 in Lower Silesia,
43.2 to 75.6 in Dortmund, 41.5 to 72.9 on the Left Bank of the
Lower Rhine, and 39.1 to 70.9 in Aachen. The proportion of
hewers (full-time workers) varied therefore between 22.6 percent. in Upper Silesia and 57.1 per cent, in Dortmund \
These proportions are, of course, not strictly comparable.
For example, the British figures are based on the manshifts'
worked at the coal face and all manshifts worked underground ;
the Belgian on man-days worked by hewers and all underground
workers ; and the Prussian figures on full-time hewers and
full-time underground workers.
It is known, moreover,that the term " hewer " has very different meanings in the
several countries.
If casualties by falls of ground are related to all work
performed underground, the rates in countries with a lower
proportion of hewers will necessarily work out lower than in
countries with a higher proportion of hewers.
The same holds good for haulage casualties, the number of
which evidently depends on the proportion of haulage men, or
rather on the time worked underground in places where haulage
casualties may occur 2.
1
Sixth Annual Report of the Secretarti for Mines, 1926, p. 141 ; London,
1927. •—• Statistique des industries extractives et métallurgiques, 1926,
Table II; Brussels, 1927.—Zeitschrift für das Berg-, Hütten- und Salinenwesen im Preussischen Staate 1924, p. 206; Berlin, 1924.
2
An instance may nevertheless be given for falls of ground. The
Belgian and British rates of fatal casualties caused by falls of ground
in 1925 per thousand workers underground were 0.44 and 0.61 respectively, the thousand workers representing the average number of
workers present in Belgium and the average number of workers employed

— 60 —
Haulage casualties may happen to all kinds of underground
workers, though mainly, of course, to haulage men. Moreover,
the classifications in some countries are based on a local criterion,
the haulage roads and blind shafts, etc. (Prussia, etc.) ; in
others, e.g. in Great Britain, on the operations of haulage ; in
Belgium, haulage casualties in blind shafts (puits intérieurs)
and working shafts are given under these headings.
. One conclusion only can be drawn from the rate by causes :
a fairly great regularity within each country which is not to be
found with other causes. Fatal casualty rates by gas and coal
dust, for instance, show far more considerable changes from
year to year.
As regards causes of non-fatal casualties, the definitions of
reportable non-fatal casualties are generally too different to
allow of any conclusions, except for Great Britain, Prussia and
France, where the limits are three or four days respectively.
Rates by causes, however, are calculated only in France for
non-fatal casualties, and in Prussia for total casualties. As
fatal casualties are only a small percentage of all casualties,
the inclusion of the former would not greatly impair comparability. It may be noted that contrary to what was found with
fatal rates, total casualty rates by falls of ground are lower in
Prussia than in France. In 1926, the Prussian rate by falls of
ground was 83.67 per 1,000 full-time workers underground and
the French rate 170.5 ; the haulage rates were 93.48 and 83.53
respectively. As the limit for reportable casualties is even
lower in Prussia than in France, and as the application of
similar methods for calculating exposure would rather lower
the Prussian rate, it is difficult to offer an explanation.
So far as non-fatal casualty rates are available, they too show
a certain regularity within the countries for falls of ground and
haulage casualties.

in Great Britain. If Belgian rates are calculated for fatal casualties
by falls of ground for hewers only (dans íes tailles, travaux préparatoires
et galeries horizontales ou inclinées en veine, au cours ou à l'occasion du
travail d'abattage ou de creusement) per 100,000 man-days of hewers,
and British rates for casualties by falls of ground at the working face
per 100,000 manshifts worked at the coal face, the Belgian rate works
out at 0.58 and the British rate 0.30, the relation being contrary to that
of the average worker rates. It must, however, be kept in mind that
falls of ground in all kinds of shafts are excluded in the Belgian average
worker rate for falls of ground.
The British rates per manshifts do not include casualties of workers in
ironstone mines, which are included in the rates per average number
of workers.

— 61 —
Percentages by Causes
Comparison of percentages by causes, besides being impaired
by differences in classification, and though independent of the
methods of calculating exposure to risk, does not afford any
measure whatever of the actual incidence of risk, as a higher
percentage for one cause lowers the percentages for other causes.
Thus the high percentage of haulage casualties in Prussia greatly
reduces the percentage for falls of ground.
Two facts, however, may be derived from the table giving
percentages by causes for fatal casualties in 1920, 1921 and
1922.
(1) The percentages for falls of ground and the percentages
for haulage accidents are highest and very constant
within each country.
(2) Though percentages for falls of ground and for haulage
accidents vary considerably as between the different
countries, the two percentages together are fairly uniform, oscillating between 60 and 80 per cent., being
usually somewhere near 70. Belgium is found to form
an exception, but the lower percentage for haulage
casualties and falls of ground is most likely due to the
inclusion of many such casualties among shaft accidents, which include all such casualties in main shafts,
blind shafts and working shafts. The percentage for
shaft casualties in fact amounts to between 22 and 27
per cent, in this country.
It will be seen, moreover, from the national tables given in
the Appendix that neither rates nor percentages for falls of
ground and haulage casualties have declined.
Rates for other causes as well as percentages differ widely
as between countries and vary most considerably from year to
year.
Percentages for causes of non-fatal casualties, which have
been calculated for Great Britain and France, together with
percentages by total casualties in Prussia, so far as available,
show much the same features. Percentages for falls of ground
in the different countries agree more closely even than those
for fatal casualties, and the variations within the countries
both for falls of ground and haulage casualties are considerably
less than in the case of fatal casualties.

COAL M I N I N G : FATAL CASUALTIES U N D E R G R O U N D

Percentages by Causes, 1920-1922, in Different Countries
Country
and
year

Falls of ground

India
1922
United States
Great Britain

Gases and coal
dust

Explosives

Shaft accidents

Miscellaneous

All causes

Number Per cent. Number Per cent. Number Per cent. Number Per cent. Number Percent. Number Per cent. Number Per cent.

1920
United States 1,132
Great Britain
544
Belgium . . . .
55
505
7S
India
71
1921
United States
Great Britain
Belgium

Haulage

All causes
rate per
1,000 men

54.53
56.37
36.92
35.71
49.37
48.30

408
237
25
487
17
16

19.65
24.56
16.78
34.44
10.76
10.88

182
26 1
14
103
9
6

8.77
2.69
9.39
7.28
5.69
4.08

128
22
7
68
6
8

6.16
2.28
4.70
4.81
3.80
5.44

56
40
39
130
28
28

2.70
4.14
26.17
9.19
17.72
19.05

170
96
9
121
20
18

8.19
9.96
6.04
8.57
12.66
12.25

2,076
965
149
1,414
158
147

100
100
100
100
100
100

4.32
0.97
1.34
2.94
12.00
1.39

1,024
383
53
444
61
150

54.85
56.16
40.46
35.40
42.36
61.73

341
170
23
424
24
32

18.26
24.93
17.56
33.81
16.67
13.17

125
19
18
179
26
15

6.69
2.78
13.74
14.27
18.05
6.17

152
13
1
54
6
18

8.14
1.91
0.76
4.32
4.17
7.41

36
26
35
76
16
18

1.93
3.81
26.72
6.06
11.11
7.41

189
71
1
77
11
10

10.13
10.41
0.76
6.14
7.64
4.11

1,86 V
682
131
1,254
144
243

100
100
100
100
100
100

4.73
0.98
1.16
2.40
10.30
1.39

905
551
39
435
72
105

49.16
55.16
36.79
39.30
54.14
56.15

341
211
20
391
13
14

18.52
21.12
18.87
35.32
9.77
7.49

320
73
9
68
3
21

17.38
7.31
8.49
6.14
2.26
11.23

92

5.00

142

3 QO

108

21.70
7.41
14.28
17.11

7
84
18
8

7.71
10.81
6.60
7.59
13.53
4.28

1,841
999
106
1,107
133
187

100

1.70

41
39
23
82
19
32

2.23

17

5.51
1.07
Î.02
2.42
8.60
2.18

1

8
47
8
7

7.55
4.24
6.02
3.74

Exclusive of suffocation.

100

1ÖÖ
100
100
100

^
C
CD

U
s*

ce
CD

—H

S

5

O O O
O O O
H r l r l

TH lOCO
C O O O

CD 00 i-i
IO O S O
O I O OS

" * l H CO
0 0 TH T - I
CM^tCM

oo Tf oo
io o o o

•Û

g
£

CD

C O O X

00 T t 1 - *
O CO CM

io e o o

THCMCO

iqqoo
osco od

O T H OS
CO TH O
O T T 00
CO'iO r i CM CM CM

T-t

- * 0 0 CO

eòo-*

0)
Pi

COCOCO

CD

COCOCO

io io os

CO OSCO
CM T H T H

X!

THCM

s

3

T H O C M

" * • * IO

l-(

s
u

O

T H C D TH

O O C D

±»
Cß

3

£
+3

a
o
«
w
0

o o o
o
o o
H r l r l

0)
CU

03
o

Q
Z
¡3
O

o o o
o
T HoH o
H

mono

IO e o o

COCMiO

THTHCM

O

TH TH

«¿

CD

I O I O O

a
2
'S

ÎJ

- * l > IO

0 0 I - I CM
CM CO OS
OS OS 00

odd

odo

-*OsO
X X
O
- * l O CS

T H - * co
00 co co

Ö
CD
ö

l O OS 0 0
r-lLO^f

O O O O

CD
0-

CD
04

COCM-tf
CMC33 1 0
Tf 0 0 - *

CMTHCO
oo oo T - I

00

O O O
T H CM
CDiOO
COTHTf
TjlHOS
CO CO CM

t3

CD

ä

, Û

«

z
o

S

¿2

«

I O CO CO
OOSCM
O T-^Tf

correr

THCMCM

C/l

W
H
•—,

X
CO

r-l

<

D

03
<U

-«
U

a

tfl

J
<•

«
U

'cfj

O
P.
X

cu

rf ed

•4

t,

o o

H

<
h

V¡

<s>
53

ÓÓÒ

00 i O CM
CMCMIO
CM-ri CM

rf CMO
oosoo

OCM

-W

50 _ ^

tí
CD

00T»<IO

COCOCM

THCD TH

O O O CD
TH O O

n
o »
O T H CO

CD

odd

io eoo
ooq
odo

- * ! D H
THCOTH
TH
T-l

C M O T H
CM T - I

I O IO co
CO O TH
CM
CO

if O M
lOO^f
CMCOlO
OCMO
CM CM CM

C O O X

TH TH O
O C M T H

T H O C O

'O o
OH

«M

CD

Ss

tí

ri
O

!*3

Z
O
Z

•frj

THOÓOÓ

THCMOS

l O O O
00 i o t >

OcOrt<
T H OSCO
TfOCM

a
¡z¡

00l>co
C l H l f

O O S O

COCO T H

co

OOCM^IO0t>TJH

0 0 O O
COCOCD
OS CM CO

m
ono
I O O C O

oô
do
COCOCO

-*
co d
CO-*rf

OS CM CO*
CMCOCO

r-l CD 0 0
COOCM
OOSOS

- * -* o

cooco

H O N
- * COCO

- * 0 0

Ü

O

t.
as

OQ

scej
fa

S
3

a
u

«
(S
M

O T H C M

CMCMCM
OS OS OS
T-l I H T - I

T-l TH T-l

'»«"T'a

«Sa

Ì—I

THCMCO

o - *

OS e o o
CM CM
C O - * IO
CMCMCM
OS OS OS
r l H r l

^-^
WS

>—•.

uè 2
fe

Ü

•*

-*CMrr
N O - *

CS a l
J-" CO

CS w
ti

o

THOSCM

THCMCM

O T H C M

CS +J CO
•y c s r j

O H T f

• * TJI T *
CO T - I OS

CM CM CM
Os Os OS

.S'ca'új"'

-*coco

T i

TH

i>-*q

0)
PH

"o

IOCMTH
IO o

C O N O

<3

o
•u

odd

IO O S O
CM T-l TH

^

CD

e«

X
CM
CM CO CO
O T H

co

u
CD

O
Z

odo

3
S3

i—l'-Ö

OH

odd

CD

s»

«

CM CO OS
C D - * OS
CO^CO

.Û

W

H
O
H
tó
O

oo
osco
T-l T - l T H

^ '•"î *"¡

cu
+3

- j CS CS
m O

»

3H S
ft.

The one salient fact which is borne out by the statistics is
the great importance of haulage and falls of ground among
causes of coal-mining risks ; also there is a considerable
constancy of these two kinds of risk within each country. This
might appear all the more remarkable as falls of ground are
natural phenomena, largely independent of the human factor
while haulage casualties depend exclusively on this factor.
Some suggestions, though based on very slight data only, may
be added to show that this regularity is mainly one of accidents.
In France it is found that the percentages for fatal and non-fatal
casualties by falls of ground vary inversely : higher fatal
percentages correspond to lower non-fatal percentages :
Year
1920
1921
1922

Fatal
49.37
42.36
54.14

Non-fatal
34.94
43.23
40.36

Percentages of fatal and non-fatal casualties by haulage
casualties also vary more or less inversely both in Great Britain
and France :
Great
Year
1920
1921
1922

Britain
Fatal
24.56
24.93
21.12

Non-fatal
27.25
22.30
27.55

France
1920
1921
1922

10.76
16.67
9.77

25.36
19.52
19.72

This negative correlation seems to point to the conclusion
that the regularity of percentages for falls of ground is really
one of " accidents ", the consequences of which may be fatal or
non-fatal, according more or less to hazard.
Finally, the great regularity of risks by falls of ground and
haulage is confirmed by the British rates per manshifts which
since 1922 have been calculated for casualties by falls of ground
and haulage casualties. In calculating these rates, casualties
by falls of ground have been related to manshifts worked at
the coal face, and haulage casualties to those worked elsewhere
below ground. These rates come very near to true measures
of risk, and they too show a marked constancy throughout
the five years of observation.

APPENDIX
NOTES ON T H E STATISTICS OF COAL-MINING ACCIDENTS
IN DIFFERENT COUNTRIES

BELGIUM
Accidents in coal mines are recorded both in the Annales des Mines
de Belgique and in the Statistique des Industries extractives et métallurgiques et des appareils à vapeur en Belgique, published by the
Ministry of Industry, Labour and Social Welfare.
Scope
The statistics cover all coal mines in Belgium, exclusive of ancillary
works such as washeries, briquette and cokeworks, and power stations,
for which returns are given separately. Office and technical
workers are also excluded.
The statistics include all accidents, all fatal casualties and non-fatal
casualties entailing permanent total or partial incapacity. A fatal
casualty is one leading to death within thirty days from the accident. Accidents due to pathological causes are excluded.
Data and Sources
Accidents are reported, under the Compensation Act of 1903
(24 December), by the head of the undertaking to the mine engineers.
The average number of employees for each concession is found by
dividing the man-days worked (journées de présence) during the days
when coal was wound, as obtained from the payrolls, by the average
number of days on which coal was wound. These days are, for each
mine, all days on which at least one pit was active. The total number
of coal miners is found by adding up the numbers thus obtained for
each concession. The average number of man-days worked for the
purpose of calculating rates, however, refers to manshifts worked on
all days on which the mine was open.
Accidents and casualties are classified by provinces. Fatal casualties
and non-fatal casualties as well as accidents are shown for underground
and surface separately and for underground and surface combined.
Accidents and casualties are also classified by causes.
The Annales des Mines de Belgique contain, moreover, detailed
reports for the several districts and for certain groups of causes.

— 66 —
Measures of Risk
1. Fatal casualties per 10,000 workers for underground, and underground and surface combined, are calculated.
2. Fatal casualties per 1,000,000 manshifts worked are published
in the annual tables (underground, and underground and surface
combined).
3. In the text, moreover, fatal and non-fatal casualty rates per
10,000 workers, underground, surface, and underground and surface
combined, are calculated ; for instance, in the report of 1924.
4. The number of accidents and the proportion of fatal and nonfatal casualties per accident both for underground accidents separately,
and for underground and surface accidents combined, are given in
the text.
5. Fatal casualties per 10,000 workers are calculated for main
groups of causes, both per 10,000 underground workers, and per
10,000 workers for surface and underground combined.
TABLE I.

NUMBER OF MAN-DAYS WORKED, AND NUMBER OF FATAL

CASUALTIES AND RATES PER 1 , 0 0 0 , 0 0 0 MAN-DAYS IN BELGIUM, 1 9 1 2 ,

1913 AND 1920-1926 (UNDERGROUND AND SURFACE)

Year
1912
1913
1920
1921
1922
1923
1924
1925
1926

Man-days worked
42,517,868
43,268,158
48,510,230
48,307,370
46,590,260
48,906,910
51,429,270
48,918,080
49,304,580

Fatal casualties
Kate
Number
145
152
181
146
142
175
202
147
159

3.41
3.51
3.73
3.02
3.05
3.58
3.93
3.00
3.22

TABLIí II.

NUMBER OF WORKERS PRESENT, AND NUMBER OF FATAL

AND SERIOUS NON-FATAL CASUALTIES AND RATES PER 1 0 , 0 0 0 WORKERS
IN BELGIUM, 1 9 1 2 , 1 9 1 3 , AND 1 9 2 0 - 1 9 2 6 (UNDERGROUND AND SURFACE)

Year

Number
of workers
present

Serious non-fatal
casualties

Fatal casualties
Number

Number

.Rate

Fatal and serious
non-fatal casualties

Rate

Number

Rate

9.21
7.56
6.54
5.04
5.22
8.03
6.97
5.55
5.24

222
207
220
188
160
239
248
193
193

21.08
19.56
19.98
16.61
15.47
21.80
20.84
17.56
17.44

2.97
4.30
2.81
2.75
3.85
5.56
4.32
2.38
2.62

32
42
47
29
55
52
60
27
37

7.93
10.62
9.43
5.69
11.14
10.32
11.26
5.35
7.46

254
249
267
217
215
291
308
220
230

17.43
17.13
16.70
13.23
14.07
18.19
17.87
13.72
14.36

Underground
1912
1913
1920
1921
1922
1923
1924
1925
1926

105,324
105,801
110,116
113,191
103,444
109,639
118,981
109,916
110,615

125
127
148
131
106
151
165
132
135

97
80
72
57
54
88
83
61
58

11.87
12.00
13.44
11.57
10.25
13.77
13.87
12.01
12.20

Surface
1912
1913
1920
1921
1922
1923
1924
1925
1926

40,346
39,536
49,828
50,949
49,394
50,364
53,304
50,467
49,582

20
25
33
15
36
24
37
15
24

4.96
6.32
6.62
2.94
7.29
4.76
6.94
2.97
4.84
Underground

1912
1913
1920
1921
1922
1923
1924
1925
1926

145,670
145,337
159,944
164,140
152,838
160,003
172,285
160,383
160,197

145
152
181
146
142
175
202
147
159

9.95
10.46
11.32
8.90
9.29
10.94
11.72
9.17
9.93

12
17
14
14
19
28
23
12
13

and Surface
109
97
86
71
73
116
106
73
71

7.48
6.67
5.38
4.33
4.78
7.25
6.15
4.55
4.43

— 68 —

TABLES III.

NUMBER OF WORKERS PRESENT, AND NUMBER OF FATAL

CASUALTIES AND RATES PER 1 0 , 0 0 0

WORKERS,

UNDERGROUND, BY

CAUSES, IN BELGIUM, 1920-1926
f a t a l casualties by causes
Year

1920
1921
1922
1923
1924
1925
1926

Number
of workers
present

Shaft
accidents

Coal gases and
coal dust

Falls
of ground

Number

Rate

Number

Kate

Number

Bate

38
35
23
17
28
29
29

3.45
3.09
2.23
1.55
2.35
2.64
2.62

55
53
39
55
52
48
51

4.99
4.68
3.77
5.02
4.37
4.37
4.61

14
18
9
26
44
14
15

1.27
1.59
0.87
2.37
3.69
1.27
1.36

110,116
113,191
103,444
109,639
118,981
109,916
110,615

Fatal casualties by causes (continued)
Explosives

1920
1921
1922
1923
1924
1925
1926

Number
7
1
8
8
4
6
2

Haulage

Bate

Number

0.64
0.09
0.77
0.73
0.34
0.55
0.18

25
23
20
30
27
28
29

Miscellaneous

All causes

Kate

Number

Rata

Number

Rate

2.27
2.03
1.93
2.74
2.27
2.55
2.62

9
1
7
15
10
7
9

0.82
0.09
0.68
1.36
0.85
0.63
0.81

148
131
106
151
165
132
135

13.44
11.57
10.25
13.77
13.87
12.01
12.20

— 69 —

CAxXADA
Accident statistics for the whole of the coal mines of Canada were
not published by the Dominion Government before 1926. In 1926, the
Department of Trade and Commerce, Dominion Bureau of Statistics, in its annual report, Coal Statistics for Canada, for the first time
published a table showing the fatal and non-fatal casualties in the
coal-mining industry, in Canada, by provinces. Casualties are
classified as underground and surface and by groups of causes. The
classification and the figures for 1926 were as follows :
Fatal
casualties
Underground :
Falls of roof or face
Mine cars or locomotives
Gas and dust explosives
Explosives
Electricity
Timbering
Mining and loading
Miscellaneous

I:Î

678
567
10
21
11

1
12

S)

816

73

2,121.

3.'}
14

Total
Surface:
Haulage and cars
Machinery
Miscellaneous

,

Granii total.

y

4

97
55
:¡07
459

77

2,580

,
Total

Non-fatal
casualties

CZECHOSLOVAKIA
Coal-mining accident statistics are published by the Ministry of
Public Works, section V, in the publications Hornicky Vestnik
(Mining Bulletin) and Uhli (Coal).
Scope
The former report covers all mines and ancillary works, the second
coal mines (pit coal and lignite) only.
Casualties reported are :
(1) Fatal casualties, i.e. those resulting in death immediately or
subsequently. No limitation is fixed to the period which may elapse
between accident and death in order to make the casualty reportable.
(2) Non-fatal casualties. These are : (a) " serious " casualties, i.e.
casualties serious as regards the nature of the injury, viz. those

— 70 —
resulting in mutilation of the body or permanent injury to health.
The days of incapacity to work are not taken into account, and
serious casualties need not even entail any incapacity to work.
(b) Casualties serious only as regards the duration of incapacity to work,
including those which require a treatment of more than nineteen days.
Casualties incapacitating for less than nineteen days have to be
notified, but are not included in the statistics.
Data and Methods of Computation
Fatal and serious non-fatal casualties have to be notified by the
management of the mines to the Mining Office of the district (Bassin).
These Offices send copies of the reports to the Ministry of Public
Works, which compiles the statistics.
In Hornicky Vestnik, casualties are classified by causes, underground
and surface separately. In a further table casualties are classified
by districts (underground and surface).
Moreover, casualties (underground and surface) are grouped by
the kind of mineral mined, pit-coal mines and lignite mines being
given separately, as well as a classification by fault.
A classification by the day of the week on which the casualty
happened is also given.
Fatal and serious casualties in pit-coal and lignite mines are classified
separately as " fatal ", " serious by nature of injury ", and " serious
by duration of incapacity " (underground and surface).

i

Measures of Risk
1. Casualties per 10,000 workers : (a) fatal ; (b) serious by nature ;
(c) serious by duration (all mines in Bohemia, Silesia and
Moravia).
2. Fatal casualties per 10,000,000 hundredweights of mineral
extracted (coal mines).
3. Percentages by causes (all mines).
TABLE IV ( a ) *.

NUMBER OF ESTABLISHMENTS, NUMBER OF WORKERS AND OVERSEERS

OUTPUT IN HUNDREDWEIGHTS, NUMBER OF FATAL AND SERIOUS CASUALTIES, AND NUMBEI
OF FATAL CASUALTIES PER 1 0 , 0 0 0 WORKERS
CZECHOSLOVAKIA,

1919-1925,

PIT-COAL

AND

10,000,000

HUNDREDWEIGHTS

MINES (UNDERGROUND

AND

Casualties
Number
of

Year establishments

1919
1920
1921
1922
1923
1924
1925

140
154
175
151
147
143
193

Number
Of

workers
and
overseers

68,794
78,688
80,128
75.210
71,991
72,677
64,890
1

Output
in
hundredweights

Underground
Fatal

Surface

Seri- Serious ous by Fa- Seriby
by
tal nana- durature
tion
ture

102,542,332 153 3 9 2
113,749,539 66 4 4 5
120,232,092 95 4 0 5
104,649,897 39 371
123,472,513 55 4 2 2
151,789,419 90 573
127,544,560 70 4 5 5

1,613 16 119
91
1,375 14
2,028
4 125
4 103
2,596
8 104
2,575
7 109
3,085
86
4
2,710

I>

SURFACE)
Fatti easealtin

Total

SeriSeri- Serious by Fa- ous by ous by
dura- tal na- duration
tion
ture
267 169 511
265
80 536
99 530
351
4 5 5 43 4 7 5
63 526
370
97 6 8 2
415
74 541
371

per
per
10,000 10,000,0«
work- hundred
e r s weights

1,880 2 4 . 5
1,640 10.1
2,375 12.3
5.7
2,851
8.7
2,945
3,500 13.3
3,081 11.4

Supplied by the Ministry of Public Works to the International Labour Office.

16.4
7.0
8.2
4.1
5.1
6.4
5.8

— 71 —
TABLE IV (b)

1

•

NUMBER OF ESTABLISHMENTS, NUMBER OF WORKERS AND OVERSEERS,

OUTPUT IN HUNDREDWEIGHTS, AND NUMBER OF FATAL AND SERIOUS CASUALTIES AND
NUMBER

OF FATAL CASUALTIES PER

1 0 , 0 0 0 WORKERS AND 1 0 , 0 0 0 , 0 0 0

HUNDRED-

WEIGHTS IN CZECHOSLOVAKIA, 1 9 1 9 - 1 9 2 5 , LIGNITE MINES (UNDERGROUND AND SURFACE)
Casualties
Kumbir
of

Numbs?
of

Year establishments

1919
1920
1921
1922
1923
1924
1925

229
251
266
243
231
217
151

workers
and
overseers

Output
in
hundredweights

46,121
56,480
56,885
51,449
46,020
45,611
43,349

173,229,608
199,566,103
213,351,276
191,742,961
162,655,298
204,596,902
187,891,420

Underground

Fatal easuittin

Surface

Total

per
Seri- SeriSeri- SeriSeri- Seri- 10,000
ous Fa- ous ous Fa- ous
ous work- 10,000,000
Fa- ons
workers
by
by
by
by
by
tal natal nadura- tal na- dura- e r s
durature tion
ture tion
ture tion

37
44
36
35
37
41
30

180
181
181
187
206
266
212

581
421
655
1276
1389
1486
1493

20
23
26
16
7
14
9

123
131
144
129
106
109
79

330
287
386
474
544
520
515

57
67
62
51
44
55
39

303
312
325
316
312
375
291

911
708
1,041
1,750
1,933
2,006
2,008

12.3
11.8
10.8
9.5
9.5
12.0
9.4

' Supplied by the Ministry of Public Works to the International Labour Office.

FRANCE
The Mines Department of the Ministry of Public Works (Ministère des Travaux Publics, Direction des Mines) publishes a report,
Statistique de VIndustrie Minérale et des Appareils à vapeur, en France
et en Algérie.
Scope
Statistics relate to practically all coal mines, including lignite mines,
but ancillary works are not included in the main statistics. All
fatal casualties and all casualties disabling the worker for more than
four days are registered. Casualties the consequences of which are
unknown are regarded as non-fatal.
Data and Methods of Computation
Casualties are classified as fatal casualties, casualties entailing
permanent incapacity, casualties resulting in temporary incapacity,
and casualties with issue unknown.
These casualties, as well as accidents, are subdivided as underground
and surface accidents and casualties. The former (underground) are
subdivided by summary groups of causes.
These various groups are given separately for the different districts,
but for lignite and pit-coal mines together.
The number of workers employed is found by dividing the number
of man-days worked (journées de présence) by the number of coalwinding days.
Measures of Risk
1. Fatal casualties, underground and surface combined, per 10,000
workers employed underground and surface.
2. Casualties underground per 10,000 workers underground : (a)
fatal, and (b) non-fatal.

3.2
3.4
2.9
2.6
2.7
2.7
2.0

— 72 —
3. Similar rates are calculated by causes underground for fatal and
non-fatal casualties.
4. Casualties on the surface per 10,000 surface workers : (a) fatal
and (¿>) non-fatal.
TABLE V.
NUMBER OF WORKERS PRESENT, NUMBER OF FATAL AND NONFATAL CASUALTIES, AND FATAL CASUALTY RATE PER 1 0 , 0 0 0 WORKERS,
IN FRANCE, 1 9 1 2 , 1 9 1 3 , AND 1 9 2 3 - 1 9 2 6 (UNDERGROUND AND SURFACE)

Year

1912
1913
1923
1924
1925
1926

Casualties
Number of
workers
Underground
Total
Surface
present
(underground
and surface) Fatal Non-fatal Fatal Non-fatal Fatal Non-fatal
202,365
203,306
263,995
286,562
299,133
306,878

44,954
44,716
61,889
74,504
81,895
91,128

268
184
186
234
277
266

34
34
42
47
77
53

6,553
6,813
10,564
11,710
11,621
11,892

Fatal casualties (underground
and
surface )
per 10,000
workers
14.9 1
10.7»
8.6
9.8
11.8
10.3

302 51,507
218 51,529
228 72,453
281 86,214
354 93,516
319 103,020

1

Figures calculated by the International Labour Office.
* Figures recalculated by the International Labour Office.
TABLE VI.
NUMBER OF WORKERS PRESENT, NUMBEF! OF FATAL
CASUALTIES, AND RATES PER 1 0 , 0 0 0 WORKERS, UNDERGROUND» BY
CAUSES, IN FRANCE, 1 9 1 2 - 1 9 2 6

Year

1912
1913
1923
1924
1925
1926

145,573
146,568
183,463
203,444
214,831
222,983

Year

Chains or
ropes, etc.,
breaking

Explosion of
fire-damp,
other gases,
or coal dust

Falls of
ground

Number of
workers
present

Explosives

Number

Rate

Number

Rate

Number

Rate

84
101
93
120
107
131

5.8
6.8
5.1
5.9 1
á.C1
5.8

106
14
2
3
1
2

7.3
1.0
0.1
0.1
0.0
0.1

7
3
5
12
12
12

0.5
0.2
0.3
0.6 1
0.6»
0.5

Shaft accidents

Number Rate
1912
1913
1923
1924
1925
1926

4
6
6
1
61
5

0.3
0.4
0.3
0.0
2.8
0.2
1

Haulage

Others
Sumber
17
14
31
25
29
29

. Other
causes

AH
causes

Kate Number Sate Number Hate Number Rate
1.2
1.0
1.7
1.2
1.3
1.3

28
41
30
57
48
63

1.9
2.8
1.6
2.8
2.2
2.8

22
5
17
16
19
24

1.5
0.3
0.9
0.8 1
0.9 1
1.0

Figures recalculated by the International Labour Office.

268
184
186
234
277
266

18.5
12.5
10.1
11.5
12.8
11.9

— 73 —
GERMANY
As the great majority of the German coalfields are in Prussia, the
Prussian accident statistics published in the annual report of the
'•Grubensicherheitsamt" (Safety of Mines Department), Berg-, Hüttenund Salinenwesen im Preussischen Staate, published by the Ministry
of Trade and Industry, are the main sources of information. Further,
provisional accident statistics are published quarterly in the report,
Deutscher Reichs-, und Preussischer Sfaatsanzeiger by the "Grubensicherheitsamt".
Scope
Up to 1923 only fatal casualties were reported in the statistics.
If the fatal issue of a casualty is reported after termination of the
report no rectification is made. Since 1923 all non-fatal casualties
disabling the worker totally or partially for more than three days are
included.
Casualties reported are those due to mining operations, and happening in or about the mine during the shift to the mine workers (Belegschaft). Thus the main statistics do not include :
1. Casualties due to physical or mental defects of the injured, for
instance death due to strokes.
2. Casualties due to some event not connected with mining operations, as, for instance, lightning, suicide, and murder.
3. Casualties happening on the way to and from the shift.
4. Casualties among persons other than mine workers, for whom
fatal casualties are given in a separate table.
Casualties at ancillary undertakings, as coke ovens and briquette
works, are included provided these works are under the control of the
mining authorities. They are, however, given as a separate group
among the causes of surface accidents.
Data and Methods of Computation
Casualties have to be reported by the head of the undertaking to the
local mining police within three days after the head has had cognisance
of them, according to section 1552 of the Imperial Insurance Code.
The employees to which the accidents refer are the technical
employees, and the wage earners 1. From 1921-1925 the number
of workers was represented by "full-time" workers calculated by
dividing the number of normal manshifts worked (including shorttime shifts reduced to shifts of normal length), i.e. the total shifts
exclusive of overtime shifts, by the number of working days.
Since 1926, the total number of manshifts worked, including overtime
shifts reduced to shifts of normal length is taken as basis for the calculation, a method already applied in most districts before 1921. The
number of working days consists of the calendar days after deduction of
Sundays, legal holidays and church holidays on which the mine was
completely idle. The data are derived from the official Prussian
production and wages statistics.
The tonnage to which casualties were related till 1925 was the
saleable coal as reported in the statements for production statistics
(Decree of 15 January 1913).
1
The " employees " include also those persons working for their own
account ( Unternehmer-Arbeiter) who are insured in the trade fund (Berufsgenossenschaft) of the respective mine. Not included are persons not
belonging to the mine (Betriebsfremde) and only temporarily present there.

— 74 —
Casualties are given for the various coal-mining districts by causes.
The classification by causes was somewhat changed in 1923. Since
1926, non-fatal casualties are classified by duration of incapacity
to work, as follows : casualties entailing incapacity to work of (o)
more than thirteen weeks ; (b) more than four weeks and not more
than thirteen weeks ; (c) four weeks or less.
Measures of Risk
The two main measures of accident risk employed in Prussian
statistics are :
1 Totar A and fatal casualties per 1,000 men : (a) underground,
(b) surface and (c) total.
2. Similar rates by causes.
3. Tonnage rates indicating the number of fatal casualties per
1,000,000 tons were calculated up to 1925.
Various tables on special groups of casualties, on percentages of all
casualties for fatal casualties, and percentages of total casualties by
causes, are occasionally published in the text. The tables below
relate to coal mines only.
Insurance Statistics
Accident statistics of the insurance institutions are published in
the Amtliche Nachrichten des Reichsversicherungsamtes, bui; only for the
mining trade unions generally, and not for coal mining in particular.
Moreover, accidents are compensated for by the accident insurance
institutions only after thirteen weeks of disability, as for the first
thirteen weeks benefits are paid out of the sickness insurance fund.
It is evident that rates must be much lower than in the coal-mining
statistics.
Accident rates are calculated per thousand persons insured as well
as per thousand full-time workers. The full-time worker is found by
dividing the days worked by 300. These rates are given separately
for fatal casualties, casualties entailing permanent total and partial
disability, and casualties entailing temporary disability.
Under a special heading all casualties reported — that is to say,
all casualties disabling for more than three days — are published
separately.
Casualties, though not rates, are classified according to age and sex.
Juveniles under sixteen years and adults are distinguished. Casualties,
moreover, are classified by causes according to the general scheme of
the insurance statistics which differs from the scheme of causes for
coal mining statistics.
T A B L E V I I . —• N U M B E R O F F U L L - T I M E W O R K E R S A N D T E C H N I C A L E M P L O Y E E S , N U M B E R O F FATAL C A S U A L T I E S , A N D R A T E S P E R 1 , 0 0 0 F U L L T I M E W O R K E R S A N D T E C H N I C A L E M P L O Y E E S IN P R U S S I A , 1 9 2 3 - 1 9 2 6
( U N D E R G R O U N D AND S U R F A C E )

Underground
Year

Casualties
by

all causes

1923
1924
1925
1926

Rumbar

Bato

899
942
1,180
982

2.0
2.6
3.3
2.78

Surface

Full-time
Full-time
workers Casualties
workers
by
and
and
technical all causes technical
employees
employees

447,060
362,084
362,209
353,137

Hamber

Bat«

126
148
140
111

0.65
1.10
1.10
0.91

193,188
131,153
127,254
122,181

Total
Casualties
by
all causes
Rombar

lata

1,025
1,090
1,320
1,093

1.60
2.21
2.70
2.30

Full-time
workers
and
technical
employees

640,248
493,237
489,463
475,318

— 75
TABLE VIH. —• NUMBER OF FATAL AND TOTAL CASUALTIES AND HATES PER 1,000
FULL-TIME WORKERS, UNDERGROUND, BY CAUSES, IN PRUSSIA, 1 9 2 3 - 1 9 2 6
Year
and severity of
casualties

Falls of stone
Number

Fatal casualties
1923
1924
1925
1926
Total casualties
1923
1924
1925
1926
Year
and severity of
casualties
Fatal casualties
1923
1924
1925
1926
Total casualties
1923
1924
1925
1926

By mining
tools and
machinery

Kate Number Bate

292
434
461
491

0.7
1.2
1.3
1.1

9,243
23,027
27,446
29,546

20.7
63.6
75.8
83.7

At the
working face

2 0.004
1 0.003
7 0.019
4 0.011
312
618
971
1,081

By explosives,
etc.

Number

Rate

Numbei

8
27
21
25

0.02
0.07
0.07
0.07

2,805
9,285
12,045
13,729

6.3
25.6
33.3
38.9

0.8
1.7
2.7
3.1

In main
shafts

In small blind
shafts and
slopes

dumber Rate

dumber Rate

In level
gangways
Number

Rate

68
85
77
68

0.2
0.2
0.2
0.2

186
210
217
214

0.4
0.6
0.6
0.6

87
104
99
114

0.2
0.3
0.3
0.3

1,075
2,193
2,423
2,290

2.1
6.1
6.7
6.4

3,178
5,954
7,096
7,358

7.1
16.4
19.6
20.8

9,923
20,958
24,153
25,653

22.2
57.6
66.7
72.6

By gases
and coal
dust

Mine fires

Kate Number

Rate Numbe r Rate

21
32
37
26

0.05
0.09
0.10
0.07

153
30
237
24

0.30
0.08
0.65
0.07

63
3
2
4

0.141
0.008
0.005
0.011

207
312
328
297

0.5
1.0
0.9
0.8

235
75
313
80

0.52
0.20
0.90
0.23

105
36
25
28

0.20
0.10
0.07
0.08

Other causes
Number Rate
19
16
16
12

0.05
0.04
0.04
0.03

4,171
7,953
7,413
8,532

9.30
22.00
20.50
24.20

GREAT BRITAIN
Statistics of the divisional inspectors and a general report with
statistics for mines and quarries by the Chief Inspector of Mines are
published in the Annual Reports of the Secretary for Mines and the
Annual Reports of the Chief Inspector of Mines by the Mines Department of the Board of Trade, in virtue of returns made under the Coal
Mines Act, 1911, the Notice of Accidents Act, 1906, and the Workmen's
Compensation Act, 1923.
Scope
Up to 1923 the statistics covered all fatal and non-fatal accidents
causing incapacity to work for more than seven days. From 1924 onwards all accidents disabling for more than three days were included
in accordance with the new provision of the Workmen's Compensation
Act of 1923. Moreover, accidents by which the worker is " seriously "
injured have ot be reported to the Divisional Inspector of Mines

irrespective of the duration of incapacity, according to the Coal Mines
Act, 1911 \
Data and Sources
Reports cover all mines in Great Britain and Ireland under the
Coal Mines Act, up to 1921 (inclusive) and all mines in Great Britain
only from that date onward. For some tables, accidents in stratified
ironstone mines in Cleveland, Lincolnshire and Northamptonshire are
excluded. Accidents are reported by the employers to the mining
inspectors. A fatal casualty is one leading to death within not more
than one year and one day or up to the date of the report.
The number of employees is the average number on the colliery
books as reported in quarterly statements made under the Coal Mines
Acts. They include all wage earners on the colliery books at the
specified dates, that is, officials (overmen, deputies, firemen, examiners, etc.) ; workers employed in raising or in handling coal or other
minerals ; tradesmen (mechanics, smiths, joiners, masons, electricians,
etc.) ; workers employed in washing coal on premises adjacent and
belonging to the mine, and workers employed on sidings at the pit
and on private branch railways and tramways. Workpeople employed
at ancillary undertakings, such as coke ovens, briquette works, etc.,
are not included. Moreover, clerks and salaried persons ordinarily
employed in or in connection with the management of the colliery,
or in and about its offices, are included, such, for instance, as surveyors, undermanagers and draughtsmen, weighing clerks, despatch clerks,
time-keepers and store-keepers, if wholly or mainly employed in
clerical work.
The manshifts worked are those furnished by the monthly ascertainments of the joint auditors to the district boards instituted by the
terms of the national wages agreements. They cover approximately
95 to 98 per cent, of the industry. The total number for all mines
is estimated. Manshifts include overtime and week-end shifts
reduced to normal shifts.
The minerals raised are the saleable coal as stated by the quarterly
returns under the Coal Mines Act and the minerals raised together
with coal or, in mines under the Coal Mines Act, such as ganister,
fireclay, limestone and ironstone.
Both the number of accidents and the number of persons killed or
injured, i.e. of casualties, are published. The latter are given separately for the several districts. They are classified by causes, and
since 1925 by the nature and location, as well as duration of the injury.
For 1927 casualties were classified by age-groups.
Measures of Risk]
Three measures of risk are published in the statistics.
1. Fatal casualties per 1,000 workers employed, classified by
main groups of causes, underground and surface.
2. Casualties (fatal plus non-fatal casualties) per 100,000
manshifts worked are calculated since 1922. They are classified by
districts. Rates for fatal casualties separately for the whole country
are published in the texts. Underground casualties per 100,000
1
The following classes of accidents are included : accidents causing
fracture of head or limb, or dislocation of limb, or any other serious
personal injury, accidents caused by explosion of gas or any explosive or
by electricity or by overwinding, and causing any personal injury whatever.

— 77 —
manshifts classified by three main groups of causes are given in a
special table. The three groups of causes are : falls of ground at the
working face, haulage accidents below ground, and other miscellaneous
accidents below ground. For the first group the manshifts worked
at the coal face were till 1926 taken as exposure to risk, for the second
and the third group manshifts worked elsewhere below ground. Since
1927 casualties by falls of ground and haulage are related to all manshifts worked underground, and a surface rate is calculated similarly.
3. Tonnage rates, that is, fatal casualty rates per million tons of
mineral raised.
Fatal and non-fatal casualties combined per 1,000 persons employed
are calculated for age-groups since 1927, underground and surface.
Occasionally non-fatal casualty rates per thousand employees and
100,000 manshifts have been calculated. Percentages by causes are
not usually given but were calculated for the three groups of causes
above mentioned, e.g. in 1923, by districts.

TABLE IX. — NUMBER OF WORKERS EMPLOYED, NUMBER OF FATAL CASUALTIES,
AND RATES PER 1,000 WORKERS EMPLOYED IN GREAT BRITAIN, 1 8 9 3 - 1 9 0 2 ,

1903-1912, 1913

AND

1920-1927

(MINES UNDER THE COAL MINES ACTS)

Underground
Year

Number
of workers
employed

1893-1902 1
1903-1912 1
1913 1
1920 1 a
19211
1922
1923
1924
1925
1926 3
1927

588,446
772,234
909,834
990,359
918,066
933,029
979,785
979,108
890,849
899,778
824,866

Casualties
from
all causes
Number Rate

895
1,130
1,580
965
682
999
1,179
1,087
1,028
577
1,033

Total

Surface

1.52
1.46
1.74
0.97
0.98
1.07
1.20
1.11
1.15
1.22
1.25

Number
of workers
employed

143,945
185,614
218,056
257,865
226,245
229,725
240,646
251,140
226,979
228,431
212,525

Casualties
from
all causes
Number Bate

120
145
173
138
74
106
118
114
108
72
95

0.83
0.78
0.79
0.54
0.42
0.46
0.49
0.45
0.48
0.53
0.45

Number
of workers
employed

732,391
957,848
1,127,890
1,248,224
1,144,311
1,162,754
1,220,431
1,230,248
1,117,828
1,128,209
1,037,391

1
United Kingdom.
' Figures based on statistics of first nine months.
* Figures based on statistics of first four months. Number of workers in March.

Casualties
from
all causes
Number Bate

1,015
1,275
1,753
1,103
756
1,105
1,297
1,201
1,136
649
1,128

1.39
1.33
1.55
0.88
0.87
0.95
1.06
0.98
1.02
1.08
1.09

TABLE X.

NUMBER OF WORKERS EMPLOYED, NUMBER OF FATAL

CASUALTIES, AND RATES PER 1,000 WORKERS EMPLOYED UNDERGROUND,

BY CAUSES, IN GREAT BRITAIN, 1893-1902, 1903-1912, 1913 AND

1920-1927

Year

Number of
workers
employed

By explosiona of
fire-damp
or
coal dust
Nombir Rate

1893-1902 11
1903-1912
191311
1920
1921ia
1922
1923
1924
1925
1926 s
1927

588,446 104
772,234 133
909,834 462
990,359 26
918,066 19
933,029 73
979,785 60
979,108 35
890,849 29
899,778
5
824,866 72

0.18
0.17
0.51
0.03
0.03
0.08
0.06
0.03
0.03
0.01
0.07

By falls
of
ground

Shaft
accidents

Haulage
accidents

Miscellaneous
accidents

Numbar

Kate

Number Rate

Mir

Rate

tabir

Rate

448
573
620
544
383
551
585
607
547
334
565

0.76
0.74
0.68
0.55
0.55
0.59
0.60
0.62
0.61
0.68
0.69

79
81
98
40
26
39
58
59
34
28
53

168
235
251
237
170
211
314
262
260
131
232

0.29
0.30
0.28
0.24
0.25
0.23
0.32
0.27
0.29
0.32
0.28

96
108
149
118
84
125
162
124
158
79
111

0.16
0.14
0.16
0.12
0.12
0.13
0.16
0.13
0.18
0.15
0.13

' united Kingdom.
* Figures based on statistics of first nine months.
' Figures based on statistics of first four months.

0.13
0.11
0.11
0.04
0.03
0.04
0.06
0.06
0.04
0.06
0.06

— 79 —
TABLE XI. —• NUMBER OF MANSHIFTS WORKED, NUMBER OF FATAL AND NON-FATAL
CASUALTIES (COMBINED), AND RATES PER 1 0 0 , 0 0 0 MANSHIFTS UNDERGROUND
AND SURFACE COMBINED, BY DISTRICTS, IN GREAT BRITAIN 1 9 2 2 - 1 9 2 5 *

1923

1922
District

Northumberland..
Durham
Cumberland
Lancashire, North
Staffordshire and
North Wales
Eastern Division .
South Staffordshire
South Wales and
Monmouthshire
Bristol
Forest of Dean . . .
Kent
Scotland

Manshifts
worked

Fatal and non-fatal
casualties
Number

Per 100,000
shifts

Manshifts
worked

Northumberland . .

South Wales and
Monmouthshire
Forest of Dean . . .
Kent

Number

Per 100,000
shifts .

9,947
26,284
2,223

64.3
67.2
77.6

17,066,000
45,548,000
3,139,000

10,852
28,777
2,327

63.6
63.2
74.1

32,337,000
4,468,000
83,580,000

23,486
2,747
57,592

72.6
61.5
68.9

37,200,000
5,059,000
92,905,000

27,194
3,442
68,259

73.1
68.0
73.5

2,560,000

1,290

50.4

2,885,000

1,668

57.8

60,037,000
586,000
1,723,000
1,250,000
411,000
36,531,000

40,048
310
763
509
295
20,736

66.7
52.9
44.3
40.7
71.8
56.8

66,592,000
641,000
2,083,000
1,569,000
509,000
41,336,000

44,899
346
917
788
348
23,086

67.4
54.0
44.0
50.2
68.4
55.8

280,947,000

186,230

66.3

316,532,000

212,903

67.3

Manshifts
worked

1925

Fatal and non-fatal
casualties
Number

Per 100.000
shifts

Manshifts
worked

Fatal and non-fatal
casualties
Number

Per 100.000
shifts

16,132,000
44,156,000
2,934,000

9,506
22,887
2,255

58.9
51.8
76.9

13,734,000
35,699,000
2,624,000

8,381
19,385
2,004

61.0
54.3
76.4

37,431,000
5,083,000
93,821,000

22,926
2,904
68,418

61.2
57.1
72.9

32,458,000
4,532,000
90,741,000

19,539
2,521
66,121

60.2
55.6
72.9

2,997,000

1,527

51.0

3,013,000

1,336

44.3

64,185,000
449,000
2,058,000
1,685,000
354,000
40,336,000

42,004
227
878
781
297
21,305

65.4
50.6
42.7
46.4
83.9
52.8

56,572,000
425,000
1,855,000
1,465,000
514,000
35,878,000

37,478
206
850
749
398
19,507

66.2
48.5
45.8
51.1
77.4
54.4

311,621,000

195,915

62.9

279,510,000

178,475

63.9

Lancashire, North
Staffordshire and
Eastern Division..
South Staffordshire

Fatal and non-fatal
casualties

15,459,000
39,142,000
2,863,000

1924
District

J

* Stratified ironstone mines in Cleveland, Lincolnshire and Northamptonshire are excluded, while being
included in the other tables.

— 80 —
TABLE XII.

ESTIMATED NUMBER OF MANSHIFTS WORKED AT THE COAL FACE AND

ELSEWHERE BELOW GROUND, NUMBER OF PERSONS KILLED AND INJURED, AND RATES
PER 1 0 0 , 0 0 0 MANSHIFTS, UNDERGROUND, BY CERTAIN CAUSES, IN GREAT BRITAIN,

• • ' •'

Year

1922
1923
1924
1925
1926

1922-1926

Falls of ground at the working face
Haulage accidents (below ground)
Number of persons
Estimated number
Number of persons
Estimated number
killed and injured
of manshifts
killed and injured
of manshifts
actually
worked
actually worked at
Total
Per 100,000 elsewhere below
Total
Per 100,000
coal face
ground
number
shifts
number
shifts
107,011,000
123,023,000
120,692,000
108,679,000
38,456,000

Year

1922
1923
1924
1925
1926

50,261
55,046
51,314
47,904
18,130

47.0
44.7
42.5
44.1
47.1

111,431,000
123,144,000
121,539,000
108,270,000
37,852,000

47,007
54,589
49,254
43,700
15,868

Other (miscellaneous) accidents (below ground)
Number of persons killed
Estimated number
and injured
of manshifts actually
worked elsewhere below
Per 100,000
ground
Total number
shifts
111,431,000
123,144,000
121,539,000
108,270,000
37,852,000

57,936
67,287
61,304
56,581
20,999

52.0
54.6
50.4
52.3
55.5

INDIA
Coal-mining statistics are published by the Bureau of Mines Inpection in India in the reports of the Chief Inspector of Mines. These
reports apply to the mines under the Indian Mines Acts of 1901 and
1923 which cover British India, including Baluchistan and Sonthal
Parganas. The native States, which occupy about two-fifths of the
Empire, are not included. Hyderabad has its own department of
mines which publishes an annual report.
Scope of Statistics
The Act of 1901 applied to any mine more than 20 feet deep and
extending beneath the super-adjacent ground. The Act of 1923 does
not contain this limitation. A mine includes all works, machinery,
tramways and sidings, whether above or below ground, in or adjacent
or belonging to a mine. Since 1923 " any part of such premises on
which a manufacturing process is being carried on is excluded unless
such process is a process for coke making or the dressing of minerals".
The statistics include fatal casualties, and casualties entailing serious
bodily injury. The latter are defined as injuries which involve " the
permanent loss of the use of, or permanent injury to any limb, or the
permanent loss of, or injury to the sight or hearing, or the fracture
of any limb, or the enforced absence of the injured person from work
for a period exceeding 20 days ".

42.2
44.3
40.5
40.4
41.9

— 81 —
Data and Methods of Computation
Casualties of the kind mentioned above occurring in or about the
mine as well as disasters, by which is meant accidental explosions,
ignition, outbreak of fire or eruption of water, must be reported by
the owner, agent or manager to the chief inspector through the district
or subdivisional magistrate. The persons employed to which the
fatal casualties are referred do not include the superior supervising
staff but all subordinate officials and persons employed on sidings,
loading wharfs, private railways, surface tramways and in carting.
The daily average number of persons employed (or rather present)
is found by dividing the aggregate number of daily attendances of
persons permanently and temporarily employed by the number of
days worked by the mines.
The output is the coal raised, including colliery consumption and
coal raised for coke making.
Casualties are tabulated in three ways:
1. Fatal and serious causalties are given separately below ground
and above ground for districts and mineral fields.
2. Fatal casualties are classified according to age and sex of the
worker : figures are given for adult males and females over 12 years
and children under 12 years.
3. Casualties are classified by causes.
Measures of Risk
The measures of accident risk calculated are :
1. Fatal casualties per 1,000 persons employed :
(a) underground ;
(b) open workings (since 1926) ;
(c) surface ;
(d) underground, open workings and surface combined.
[Continued on next page.
TABLE XIII. — AVERAGE NUMBER OF PERSONS EMPLOYED DAILY, NUMBER OF FATAL
CASUALTIES, AND RATES PER 1,000 PERSONS EMPLOYED, IN INDIA, 1 9 1 1 , 1 9 1 3 AND

1920-1926 (UNDERGROUND AND SURFACE)
Underground
Year

1911
1912
1913
1920
1921
1922
1923
1924
1925
1926
1

Average
number of
persons
employed
dally
68,867
77,930
84,828
102,922
108,957
107,494
108,994
115,873
110,630
115.4551

Surface

Fatal
casualties
Number

Rate

Average
number of
persons
employed
daily

136
141
175
143
237
185
312
203
173
147 1

1.97
1.80
2.06
1.39
2.18
1.72
2.86
1.75
1.56
1.272

37,731
43,462
48,214
73,021
81,690
76,861
73,607
71,215
62,510
55,173

Total

Fatal
casualties
Number Rate
12
16
10
29
20
24
20
27
13
24

0.31
0.36
0.21
0.40
0.24
0.31
0.27
0.38
0.21
0.43

Average
number of
persons
employed
daily
106,598
121,392
133,042
175,943
190,647
184,355
182,601
187,088
173,140
170,628

Fatal
casualties
Number Rate
148
157
185
172
257
209
332
230
186
171

1.38
1.29
1.39
0.93
1.35
1.13
1.82
1.23
1.07
1.00

Including open workings, which are given separately for the first time in coal statistics for 1936.
• Calculated by the International Labour office.

— 82 —
Non-fatal (serious) casualties per 1,000 workers :
(a) underground ;
(b) open workings ;
(c) surface ;
(d) underground, open workings and surface combined.
Fatal casualties per million tons raised at coal mines.

JAPAN
Coal-mining accident statistics are published in the General Review
of the Mining Industry by the Bureau of Mines, Department of Commerce and Industry, formerly the Department of Agriculture and
Commerce.
The statistics do not refer to Korea, Formosa, and Sagalia. All
accidents have to be reported by the mineowner or his representative
to the governor of the prefecture. There are forty-three local prefectures and three urban prefectures (Tokio, Kioto and Osaka), whilst
Hokkaido forms a separate district.
The statistics cover accidents on the one hand, and all casualties
on the other hand, fatal and non-fatal. Non-fatal casualties are
classified according to whether persons are seriously injured or slightly
injured. " Seriously injured " means incapacitated for more than
one week.
Casualties are classified by detailed causes, and for each group of
causes by age, that is to say, for persons under fifteen, under twenty,
and over twenty years of age, as well as by sex.
TABLE XIV.

NUMBER OF FATAL, SERIOUS, AND SLIGHT CASUALTIES, BY SEX,
IN JAPAN, 1 9 2 1 - 1 9 2 4 (UNDERGROUND AND SURFACE)

Year

Place

Underground
1921
Total
Underground
1922
Total
Underground
1923
Total
Underground
1924
Total

Fatal
casualties

Serious
casualties

Slight
casualties

Total
casualties

Men

Women

Men

Women

Men

Women

Men

Women

502
35
537

99
7
106

3,838
368
4,206

1,015
80
1,095

114,322
11,830
126,152

25,917
2,230
28,147

118,662
12,233
130,895

27,031
2,317
29,348

438
25
463

74
10
84

4,187
371
4,558

1,238
91
1,329

109,593
10,869
120,462

26,206
2,001
28,207

114,218
11,265
125,183

27,518
2,102
29,620

527
43
570

87
6
93

4,071
395
4,466

1,340
96
1,436

125,773
12,678
138,451

26,679
2,098
28,777

130,371
13,116
143,487

28,106
2,200
30,306

680
34
714

121
4
125

1,336
445
4,781

1,262
71
1,333

114,810
11,424
126,234

26,148
2,203
28,351

119,826
11,903
131,729

27,531
2,278
29,809

— 83 —

NETHERLANDS
Coal-mining accident statistics are published annually by the Chief
Mining Engineer in the Jaarverslag van den Hoofdingenieur der
Mijnen over het jaar . . .
Scope
Statistics cover all pit-coal mines in the Netherlands. They include
all fatal casualties which have led to death before 2 June, as the report
lias to be presented to the Minister of " Waterstaat " before that date.
Non-fatal casualties reported are those disabling for more than three
weeks. Only casualties are reported.
Data and Sources
Accidents are reported, under the Accidents Act of 1901, section 61,
subsection 4 (Ongevallenwet 1901, Artikel 61, vierde lid.), to the National
Insurance Bank (Rijksverzekeringsbank).
They are classified as total, fatal, and non-fatal casualties, underground and surface. Latterly casualties entailing incapacity of more
than forty-two days are separately classified.
A detailed classification by causes is given, underground and surface.
The number of workers employed is found by dividing the total
number of workers as ascertained on the fortnightly pay sheets by
the periods of payment ; sick workers, those injured by accidents,
and those absent for other reasons are comprised, but not those serving
in the forces.
Measures of Risk
1. Fatal and total casualties per 1,000 workers employed :
(a) underground and surface :
(b) underground and surface combined.
2.

Fatal and total casualties per 100,000 tons produced.

3.

Percentages by causes for total casualties.

TABLE

XV.

NUMBER

OF

FATAL

CASUALTIES

AND

RATES

PER

1,000 WORKERS EMPLOYED, IN THE NETHERLANDS, 1 9 2 2 - 1 9 2 7
(UNDERGROUND AND SURFACE)

Year

1922
1923
1924
1925
1926
1927

Undergronud

Surface

Total

Number

Kate

Number

Rate

Number

Bate

20
31
26
39
30
28

1.10
1.57
1.19
1.73
1.28
1.13

6
4
2
2
4
6

0.79
0.52
0.25
0.24
0.46
0.66

26
35
28
41
34
34

1.01
1.28
0.93
1.33
0.39
0.36

— 84 —

TABLE XVI.

AVERAGE NUMBER OF WORKERS INSURED, NUMBER OF

FATAL AND NON-FATAL TEMPORARILY AND PERMANENTLY DISABLING
CASUALTIES BY CAUSES, AND RATES PER

1,000

WORKERS INSURED

(ALL CAUSES), IN POLAND (VOIEVODIE OF SILESIA) IN
1926

1935

Causes

Power machinery, power
transmission and labour machinery . . . .
Lifts, etc., winding ma-

1925-1927
1927

Injuries

Injuries

Injuries

anent orary

anent orary

anent orary

Fatal
Fatal
cases Perm- Temp- cases Perm- Temp- cases Perm- Temp-

4

16

65

8

18

77

4

20

88

5

13

70

10

10

38

5

8

18

1

2

1

2

0

1

0

0

0

2

24

20

4

10

12

6

11

21

4
78

5
93

0

404

8
98

2
79

1
378

11
77

2
82

4
349

10
6

16
9

120
84

14
13

16
16

101
180

6
3

8
15

111
223

34
3
5

47
6
44

396
25
103

29
0
7

40
3
45

322
23
51

26
0
8

39
0
20

315
18
53

275 1,293

193

239 1,184

146

Explosions of boilers,
steam tanks, steam
Explosions of explosives
and gases
Inflammable, corrosive
burning
substances,
heated metals, e t c . . . .
Falls of ground, stone etc.
Falls of persons in shafts,
on slopes, galleries,
Loading and unloading.
Haulage by machinery,
animals and
other
means

IM

205 1,200

R a t e per 1,000 workers
1.64 2.96 13.92 243 3.01 14.90 1.83 2.57 15.06
Average number
of
workers insured . . . .

92,869

79,44()

79,664

— 85 —
POLAND
Coal-mining accident statistics are compiled by two institutions :
the Accident Insurance Fund of Lwow, for the formerly Austrian and
Russian territories, and the Accident Insurance Fund of the District
of Silesia (Voievodie) in Krolewska Huta, for the Upper Silesian part
of the Voievodie of Silesia.
The statistics of the latter institution are very detailed. They are
referred to in the following analysis.
Scope
The source of the statistics being the insurance institutions, casualties reported are those first compensated for in the year of observation
Data and Methods 0/ Computation
Casualties are classified as fatal casualties, casualties entailing
permanent (total and partial) incapacity to work, and casualties
entailing temporary incapacity only. All casualties are classified
by sex, civil status and age (adults and juveniles). The classification
by sex and civil status is also applied to the different categories of
casualties.
A classification by nature and location of injury, going into great
detail, is made.
Casualties (total) are classified by fault. Six main groups are
distinguished : (1) fault of fellow-workers ; (2) dangerous operations ; (3) insufficient measures on the part of the management ; (4)
no use made of the means of protection by the injured ; (5) lack of
attention and skilfulness (maladresse) on the part of the injured ; (6)
misfortune and unknown causes. These groups are further subdivided,
the subdivisions specifying the nature of the fault.
The classification by causes, being made for insurance purposes, is
not wholly adapted to coal-mining risks as regards the main groups,
but is largely specialised for coal mining in the subdivisions. We
have therefore in the appended classification summarised the groups
of causes which are of little significance for coal miners and reproduced
the subdivisions of interest for coal-mining statistics.
The workers covered by the statistics are the average number of
workers insured in the year of observation.
Measures of Risk
1. Fatal casualties per 1,000 persons insured.
2. Casualties entailing permanent incapacity per 1,000 workers
insured.
3. Casualties entailing temporary incapacity per 1,000 workers
insured.

— 86 —

UNITED STATES OF AMERICA
The United States Bureau of Mines, formerly of the Department
of the Interior, and, since 1 July 1925, oi the Department of Commerce,
started publishing coal-mine accident reports in 1912. In 1913 the
Bureau published a report covering all fatal accidents described in
the State inspectors' reports beginning with 1896. In 1916 the
Bureau published all fatal accidents described in the inspectors'
reports from the beginning of the inspection service. State inspection
began in Pennsylvania in" 1869. Data regarding major explosions or
fires in pre-inspection years back to 1839 were given for some States.
From 1889 to 1909, inclusive, States reporting accidents comprised
the coalfields whose production represented 90 to 99 per cent, of the
nation's total output of coal. From 1910 onward the States reporting
accidents include all States producing coal. Accident statistics are
now regularly published in the report entitled Coal-Mine Fatalities in
the United States.
Scope of Statistics
The United States statistics comprise fatal accidents only as the
State reports are incomplete and of different scope with regard to
non-fatal accidents. The inspectors' reports publish non-fatal accidents under various forms. The introduction of workmen's compensation has led to more complete records in recent years.
All fatalities not directly attributable to the coal-mining industry
are eliminated, such as accidents in coke ovens, briquette making,
milling or smelting. Office work is excluded from the statistics.
Technical employees are included if the duties of such employees
expose them to mining hazards.
Data and Sources
Data are derived from various sources. Fatal accidents are compiled from the State mine inspectors' monthly summaries furnished
to the Bureau of Mines. They include those deaths that had resulted
when the State mine inspector furnished his summary. The monthly
reports are revised currently during the year, and further revised
after the year is closed.
Yearly data on production (since 1820) on the number of men
employed (since 1889), the number of days worked (since 1890) and
data on mining machines in use (since 1896), and the percentage of
coal mined by machine, are derived from the Annual Volumes of the
Mineral Resources of the United States, published by the United
States Geological Survey. This division of the Geological Survey
was transferred to the Bureau of Mines on 1 July 1925. Data on
mining methods were taken both from the State mine inspectors'
reports and from the United States Geological Survey.
Since 1912 accidents have been published for each State and for
each month. They are classified be detailed causes.

— 87 —
Measures of Risk
Four different kinds of frequency rates have been published by the
United States Bureau of Mines :
1. Fatality rates per average number of workers employed. As
some of the State mine inspectors' reports gave the number of employees for fiscal years and, moreover, some States included cokeoven employees, the number of employees from 1889 onward were
those calculated by the United States Geological Survey, except for
the years 1909-1911.
2. Frequency rates per thousand 300-day workers are calculated
irrespective of the length of the working day. These rates are specified according to underground and surface working. As the United
States Geological Survey did not originally publish figures for underground and surface employees separately, the proportion of underground and surface workers was calculated on the basis of the proportion found by the Bureau of Mines in 1911. Data of underground
and surface workers, however, are now published separately by the
United States Geological Survey.
3. Frequency rates per thousand 2,000-hour workers were calculated for 1903 to 1913 and have been continued until 1925. Now,
rates per million hours worked are given.
4. Normal fatality rates by causes, per million hours of labour
and per million tons "of coal which are calculated by excluding fatal
accidents caused by mining disasters killing five or more than five
persons, are published for bituminous coal mines.
5. Fatality rates per million hours of labour are calculated for
groups of causes. Underground, shaft, and surface accidents are
given separately. Accident rates are calculated, first, in relation
to total hours of exposure underground ; second, in relation to total
hours of exposure on the surface ; and third, in relation to total hours
of exposure underground and surface combined. For 1925, rates per
million men-hours worked, by causes, were calculated for each State,
back to 1911. Now, rates per 1,000 300-day workers by more detailed
causes are given.
6. Fatality rates per million short tons of coal raised are calculated
from 1870 onwards and the production of coal per death is also
computed.
7. Percentages of total fatalities by causes are published regularly.
8. Fatality rates, normal, exceptional and total, have been computed for groups of States, classified according to the percentage of
coal mined by machine (see Bulletin No. 115, published in 1916).
Methods of Calculation and Collection
The United States Bureau of Mines obtains its data from the owners
(producers') written reports, which are collected by correspondence
and supplemented by visits of field agents.
The Bureau of Mines has, however, no power to enforce these records.
The so-called commercial mines, those producing at least 1,000 tons
(per year) and working more or less steadily year after year, receive
schedules of enquiry by mail. For smaller mines, the railroads sometimes supply data on the coal conveyed, from which estimates as to
the number of men employed are made.
For the so-called " sporadic wagon mines", satisfactory results
can not be obtained by mail. The Bureau therefore asked the railroads in 1920, 1922 and 1923 to furnish lists of the wagon mines which

— 88 —
had conveyed coal to indicate the dates of opening and closing of the
mines, and the number of car loads conveyed. In years of depression,
however, most wagon mines are out of business and records are not
kept. No reports as to the number of employees or the time worked
by wagon mines have ever been obtained.
The number of men employed is not calculated according to any
common method. No records of man-days are kept by bituminous
coalowners at most mines for tonnage workers, that is, those paid
on piece rates. It was found that most of the figures reported represented the number of men commonly dependent on the mines for
employment, that is, those reporting for work when the mine started,
plus absentees, and not the average number of men actually working
at any one time, nor the aggregate number during the j r ear, nor the
absolute average number of men on the payrolls.
The days worked by the mine are the total number of full days
the mine was in operation and raised coal (tipple days), part of days
being reduced to equivalents in full days. The averages for States
are weighted by the number of men employed in each mine x.
The hours of labour refer to the " number of hours that the mines
are supposed to be in operation, cars and orders permitting, and not
the number of hours the mine actually worked ". The tonnage men
are piece workers and not obliged to put in a certain number of hours.
The figures given therefore really indicate " the number of hours
the men had an opportunity to work during a full day on the assumption that there was a full run of cars and that the market conditions
were favourable to full time operation. They do not mean that all
the tonnage men worked the number of hours stated ".
The Bureau of Mines calculates the 300-day workers by multiplying
the average number of workers in each State by the days the mine
was in operation in that State during the year. The 2,000-hour
worker is found for each State by multiplying the number of workers
by the number of hours per day in the respective mines, that is, the
number of workers in the eight-hour mines is multiplied by eight, in
the nine-hour mines by nine, and so on, and multiplying these products
by the number of days the mines were in operation. The total is
divided by 2,000. The rates per thousand 300-day workers and per
million man-hours are calculated separately for underground workers,
including shaft workers, and for sarface workers. Recently, attempts
have been made to calculate severitv rates.

1
UNITED STATES GEOLOGICAL SURVEY : Mineral Resources of the
United States, 1922, p. 401. (In 1925 the division of the United States
Geological Survey handling this work became a part of the Bureau of
Mines.)

— 89 —

TABLE XVII.
ACTUAL NUMBER OF MEN EMPLOYED, NUMBER OF 300-DAY
WORKERS, AVERAGE DAYS ACTIVE, TOTAL HOURS WORKED PER DAY, NUMBER OF 2 , 0 0 0 *
ÎOUR WORKERS AND NUMBER OF FATAL CASUALTIES AND RATES PER 1,000 EMPLOYEES,
'ER 1,000 300-DAY WORKERS AND PER 1,000 2,000-HOUR WORKERS IN THE UNITED

STATES, 1911-1913 AND 1920-1927
Men employed
Year

Actual
number

300-day
workers

Average
days
active

1911
1912
1913
1920
1921
1922
1923
1924
1925
1926
1927

728,348
722,662
747,644
784,621
823,253
844,807
862,536
779,613
748,805
759,033
757,000

534,122
541,997
593,131
601,283
474,529
405,056
560,646
499,896
480,227
559,426
—

220
225
238
230
173
144
195
192
192
221
—

Fatal casualties
Total hours 2,000-hour
worked per workers
per 1,000 per 1,000 per 1,000
Number empday
300-day 2000-hour
loyees workers workers
6,136,211
6,149,053
6,333,895
6,309,400
6,622,765
6,805,520
6,954,302
6,288,930
6,043,406
6,121,449
—

674,983
691,768
753,734
725,581
572,869
489,997
678,044
603,737
580,167
—
—

2,656
2,419
2,785
2,272
1,995
1,984
2,462
2,402
2,234
2,518
2,224

3.65
3.35
3.73
2.90
2.42
2.35
2.85
3.08
2.98
3.32
2.94

1
Calculated by International Labour Office, as discontinued in report.
orked: 1.68.

4.97
4.46
4.70
3.78
4.20
4.90
4.39
4.80
4.65
4.50
—

3.93
3.50
3.69
3.13
3.48
4.05
3.63
3.98
3.85
3.72 !
—

Kate per million hours

— 90 —
TABLE

XVIII.

NUMBER

OF

DAYS OF LABOUR PERFORMED, AND OF

300-DA

WORKERS, NUMBER OF FATAL CASUALTIES AND RATES PER 1,000 300-DAY WORKER
IN THE UNITED STATES, 1 9 1 1 - 1 9 1 3 AND 1 9 2 0 - 1 9 2 6 (UNDERGROUND AND SURFACI
Underground

Surface

Year

of Fatal
Days of labour Number
casual300-day
performed
ties
workers

1911
1912
1913
1920
1921
1922
1923
1924
1925
1926

133,283,700
135,251,775
148,061,942
144,236,367
118,297,091
100,211,422
139,429,422
125,279,912
120,654,263
140,857,480

444,279
450,840
493,540
480,788
394,324
334,038
464,765
417,599
402,181
469,525

TABLE XIX.

Kate per
per
of Fatal Bate
Days of labour Number
1,000
1,000
300-day
casual- 300-day
performed
300-day
workers
ties
workers
workers

2,486
2,220
2,624
2,077
1,875
1,846
2,304
2,264
2,107
2,400

5.60
•;-.92
5.32
¿.-.32
4.75
5.53
4.96
5.42
5.24
5.11

26,952,860
27,347,175
29,877,330
36,148,575
24,061,600
21,305,400
28,764,316
24,689,068
23,413,969
26,970,252

89,843
91,157
99,591
120,495
80,205
71,018
95,881
82,297
78,046
89,901

170
199
161
195
120
138
158
138
127
118

NUMBER OF MAN-HOURS WORKED, NUMBER OF FATAL

CASUALTIES, AND RATES PER MILLION MAN-HOURS, UNDERGROUND BY
CAUSES, IN THE UNITED STATES, 1 9 2 1 - 1 9 2 6

Year

Falls
of roof or
coal
Her

1921
1922
1923
1924
1925
1926

Year

1921
1922
1923
1924
1925
1926

1,025
908
1,167
1,062
1,080
1,214

Haulage

Kate
1.077
1.123
1.038
1.053
1.111
1.069

Electricity

Kjnber

Rate

fallir

Rate

Number

0.358
0.422
0.367
0.351
0.372
0.381

126
Sil
372
536
345
422

0.132
0.385
0.331
0.531
0.355
0.372

142
93
115
99
102
96

0.149
0.115
0.102
0.098
0.105
0.085

80
74
75
80
84
96

1

Other causes

Explosives

Rate

tab«
341
341
413
354
361
433

Gas or
dust
explosions

Shaft accidents

All causes

Number

Rate

Number

Rate

Number

Rate

125
78
116
104
101
104

0.131
0.096
0.103
0.103
0.104
0.091

36
41
46
29
34
35

0.038
0.051
0.041
0.029
0.035
0.031

1,875
1,846
2,304
2,264
2,107
2,400

1.969
2.284
2.049
2.244
2.168
2,114

Rate
0.084
0.092
0.067
0.079
0.086
0.085

Man-hours
worked
underground

952,084,500
808,173,400
1,124,171,900
1,008,690,500
971,756,300
1,135,436,100

1.89
2.18
1.62
1.62
1.50
1.94
1.65
1.68
1.63
1.31