How Calculated: Number of papers (h) that have received at least h citations.
As an example, an h index of 10 means that among all publications by one author, 10 of these publications have received at least 10 citations each.
Hirsch argues that the h index is preferable to other single-number criteria, such as the total number of papers, the total number of citations and citations per paper. However, Hirsch includes several caveats:
- A single number can never give more than a rough approximation to an individual’s multifaceted profile;
- Other factors should be considered in combination in evaluating an individual;
- There will be differences in typical h values in different fields, determined in part by the average number of references in a paper in the field, the average number of papers produced by each scientist in the field, and the size (number of scientists) of the field; and
- For an author with a relatively low h that has a few seminal papers with extraordinarily high citation counts, the h index will not fully reflect that scientist’s accomplishments.
Since Hirsch introduced the h index in 2005, this measure of academic impact has garnered widespread interest as well as proposals for other indices based on analyses of publication data such as the g index, h (2) index, m quotient, r index, to name a few.
Several commonly used databases, such as Elsevier’s Scopus, Clarivate Analytics’ Web of Science, and Google Scholar provide h index values for authors.
Resources to Find the h index
- Google Scholar provides the h index for authors who have created a profile.
- Publish or Perish is a software program that retrieves and analyzes academic citations from Google Scholar and provides the h index among other metrics. Publish or Perish is handy for obtaining the h index for authors who do not have a Google Scholar profile.
- Scopus provides a Citation Tracker feature that allows for generation of a Citation Overview chart to generate a h index for publications and citations from 1970 to current. The feature also allows for removal of self-citations from the overall citation counts.
- Web of Science allows for generation of the h index for publications and citations from 1970 to current using the "Create Citation Report" feature.
Strengths and Shortcomings
Strengths of the h index
- The h index is a metric for evaluating the cumulative impact of an author’s scholarly output and performance; measures quantity with quality by comparing publications to citations.
- The h index corrects for the disproportionate weight of highly cited publications or publications that have not yet been cited.
- Several resources automatically calculate the h index as part of citation reports for authors.
Shortcomings of the h index
- The h index is a metric to assess the entire body of scholarly output by an author; not intended for a specific timeframe.
- The h index is insensitive to publications that are rarely cited such as meeting abstracts and to publications that are frequently cited such as reviews.
- Author name variant issues and multiple versions of the same work pose challenges in establishing accurate citation data for a specific author.
- The h index does not provide the context of the citations.
- The h index is not considered a universal metric as it is difficult to compare authors of different seniority or disciplines. Young investigators are at a disadvantage and academic disciplines vary in the average number of publications, references and citations.
- Self-citations or gratuitous citations among colleagues can skew the h index.
- The h index will vary among resources depending on the publication data that is included in the calculation of the index.
- The h index disregards author ranking and co-author characteristics on publications.
- There are instances of “paradoxical situations” for authors who have the same number of publications, with varying citation counts, but have the same h index. As an example, Author A has eight publications which have been cited a total of 338 times and Author B also has eight publications which have been cited a total of 28 times. Author A and Author B have the same h index of 5 but Author A has a higher citation rate than Author B. See Balaban, AT. 2012. Positive and negative aspects of citation indices and journal impact factors. Scientometrics. DOI: 10.1007/s11192-102-0637-5
Is There an Alternative to the h index?: The m value
The m value is a correction of the h index for time (m = h/y). According to Hirsch, m is an “indicator of the successfulness of a scientist” and can be used to compare scientists of different seniority. The m value can be seen as an indicator for “scientific quality” with the advantage (as compared to the h index) that the m value is corrected for career length.
How Calculated: m value = h index (h )/ number of years since first paper (n).
Finding an Individual h-index Using Publish or Perish
Finding h-Index using Publish or Perish
1. The Publish or Perish site uses data from Google Scholar. An explanation of citation metrics is available here.
2. Publish or Perish is available in Windows and Linux formats and can be downloaded at no cost from the Publish or Perish website.
3. Once you have downloaded the application, you can use Publish or Perish to find h-Index by entering a simple author search. You can exclude names or deselect subject areas to the right of the search boxes to help with disambiguation of authors.
4. The h-Index will display on the results page.
5. You can narrow your search results further by deselecting individual articles. The h-Index will update dynamically as you do this.
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