Dummy OMI values for 2013-2019 and 2020 in Beijing
      Min     Max       Mean     
BF  35.624   49.617    41.336       
DF  22.685   32.358    25.729
AF  24.325   33.284    29.347

BF  14.380   50.285    30.671      
DF  8.085    22.784    13.445
AF  8.074    21.694    14.363
