What is the h-index and what are its limitations? Or: Stop using the h-index [Talking Head]

Educational video (talking head) on the h-index by the ScholCommLab

This short talking head video explains the h-index, a widely used metric in academia. It breaks down what the h-indexis, how its is calculated, and its common uses and limitations. Whether you're a student, researcher, or just curious about academic metrics, this video provides a clear and concise introduction to the h-index.

Educational content and script: Stefanie Haustein, Maddie Hare, Heather Woods, Isabelle Dorsch, Carey Ming-Li Chen 
Production and editing: Maddie Hare, Stefanie Haustein 
Talking head and narration: Sarah Komendat
Audio: Jonathan Degan, Marie-Josée Archambault

This video is licensed under a Creative Commons CC-BY license: https://creativecommons.org/licenses/by/4.0/

The video was created with funding from an Insight Grant (435-2021-0108, PI Haustein) from the Canadian Social Sciences and Humanities Research Council (SSHRC).

Excerpts from the script:

Bibliometric indicators, such as the h-index or impact factor, are frequently applied in academic promotion and funding decisions and can make or break researchers’ careers. Still, many academics do not fully understand how bibliometric indicators are calculated or the many factors that influence them. In this video I will teach you about one of the most used indicators in bibliometrics: the h-index. I will describe what it is, how to calculate it, and explain how it is used. Most importantly, I will address the limitations associated with using it. By the end of this video, you will be able to define and calculate the h-index and be aware of its limitations. The h-index was created in 2005 by physicist Jorge Hirsch with the goal of creating a metric that would combine an author’s number of publications and citations. The h-index is widely used, probably because it is both simple and widely available in many databases like Web of Science, Scopus or GoogleScholar. The h-index is often used in decision-making for hiring, promotion, tenure, funding, and academic prizes, either directly integrated into the selection process or used “behind the scenes” by committee members. Let’s discuss how the h-index is calculated. The h-index focuses on individual authors and aims to combine their scientific productivity using two variables. The first is the number of publications an author has published, and the second is the number of citations those publications have received. Therefore, “A scientist has index h if h of his or her Np papers have at least h citations each and the other papers have less than or equal to h citations each.” Since an author’s h-index can never exceed their number of papers they have published, the number of publications is the limiting factor. On the other hand, an author needs to have many publications in order to get a high h-index, but a high number of publications will not automatically result in a high h-index unless they are also cited frequently. Now that we have discussed what the h-index is and how it is calculated, it is important to consider some of its limitations. As a quantitative indicator based on the number of publications and citations, the h-index – like other bibliometric indicators – is not an accurate measure of research productivity and impact. It is also important to know that the h-index does not account for differences between research fields. Academic disciplines have different publication and authorship practices. While fields such as Engineering often include several, sometimes dozens, of authors on a publication, authors in disciplines such as English or History tend to work alone. This affects the average number of publications per author. Similarly, the extent to which researchers publish in books rather than journals differs between disciplines, which influences the number of publications commonly captured by the h-index. The length of reference lists also varies from one field to another. This directly influences the average number of citations per article and therefore the h-index. Disciplinary norms and publication practices affect the average number of publications per author and citations per paper, causing h-indexes to be lower in some fields than others. Since the h-index does not account for these field-specific differences, it should never be used to compare researchers from different disciplines. Like all bibliometric indicators, the h-index depends on the database used to compute it. The more publications and citations a database indexes, the higher the h-index. Databases such as Scopus and Web of Science, as illustrated in this visual, will rely on different sets of publications and citations to calculate the h-index, meaning the h-index of the same author may vary across databases.