Career Development: Know your H-Index

The H-index is increasingly being used to evaluate scholarly productivity and as one or many factors in tenure and promotion decisions.  The H-index is a measure of the number of times articles written by a scholar have been cited. Knowing your own H-index and understanding the various quirks in how the H-index score is arrived can be important for managing your career.

A scholar with an H-index of X has published X papers which have each been cited X or more times.   Thus a scholar with 100 publications and an H-index of 10, has 10 papers that have been cited at least 10 times and 90 papers cited less than 10 times each.  A scholar who published 6 papers that were cited 300 times each, has an H-index of 6. Thus, both the number of citations and the number of publications influence a scholar’s  H-index.

In general the H-index increases with the number of years a scholar has been active and the contribution any journal article makes to your H-index is a function of time since its publication. If your institution factors H-index scores in tenure and promotion decisions, publishing in the first years of your faculty appointment is critical for building an H-index. Papers published in the year or so prior to your tenure or promotion review are not likely to improve your H-index.  As a general guide for my own publishing, I assume that the number of years it will take a journal article to garner X citations is equal to X / the journal’s Impact Factor.  A journal’s Impact Factor is a measure of the average number of citations that articles in that journal garner per year, and I assume that my publications in any given journal will perform as well as the average for that journal.

Your H-index can be calculated via ResearcherID at Web of Knowledge, Scopus or Google scholar.  but since each of these services uses a different underlying database and different journals, your H-index will vary across platforms, with Google Scholar usually providing the highest H-index.  I have a paper published in BMI Complementary and Alternative Medicine that has been cited 41 times, but this journal is not included in Web of Knowledge and so does not contribute to my H-index as measured by ResearcherID.  Lokman et al., have studied the differences in the databases used by these three platforms. They found that: Web of Knowledge has extensive coverage of journals but does not cover high impact conferences; Scopus has poor coverage of journals before 1996, but better coverage of conferences; and Google Scholar has better coverage of conferences, but poor coverage of publications prior to 1996.  My non-systematic experience is that Google Scholar does a better job than the other two platforms of covering citations that appear in reference lists in scholarly books and dissertations.

The H-index does not take into account the number of authors on a paper and it has been suggested that papers that have more authors tend to garner more citations.  So that senior faculty member who did little, to no, work on the your paper but demands authorship might actually be doing you a favor.  This feature of the index tends to favor papers with experimental results that have many authors over theoretical papers that usually have fewer co-authors.  Since review, meta-analysis and systematic review papers tend to get lots of citations these types of papers can help your H-index.

The H-index also ignores placement of authors in the line-up of authors, which in some fields provides important information on an author’s contribution to a work.  For the purposes of H-index calculation appearing as the 5th author in a paper with 10 authors is equivalent to being the first author of that paper.

For a paper that is a few citations below X and thus is not yet pushing your H-index forward, you may be able to spur interest in the work by posting about the topic in relevant blogs or forums such as ResearchGate.  Of course self-citation helps too, as generally H-index scores include self-citations. As I was told – if you can’t be bothered or interested enough to cite your own work, then who will be?

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