What is the h-index?

The h-index (or Hirsch index, named after physicist Jorge E. Hirsch, who first suggested the idea) measures the impact of a particular author of a paper rather than that of the journal in which that article was published, as the journal impact factor does. The h-index equals the number of papers (h) that have been cited at least h times. For example, an author with an h-index of 5 has five papers that each have been cited at least five times.

How to find an h-index

Web of Science, Scopus, and Google Scholar all calculate the h-index for author profiles.

Web of Science

For Web of Science you can search by Topic or by Author. After searching, click on the author of interest’s name to generate a list of all their works. Then click on “Citation Report” in the top right corner. This will bring you to a report that includes the author's h-index.

An alternative way to find an h-index on Web of Science is to search for an author's name in a basic search and then select the relevant author names using the filter panel on the lefthand side. After refining that list by the name of interest and all alternative spellings, change the sorting preference at the top of the search results from "Relevance" to "Citations: highest first." Now scroll until the article number matches the citation number. That number would be author's h-index. If there isn't an exact match, scroll until the times-cited number is less than the article number. Then go down one article number, which would also be the author's h-index.

Scopus

To find an author's h-index in Scopus, select the “Authors” tab to search by name or ORCID. If searching by name, affiliation can be added to the query. The search results will show the h-index in the third column. To get a more detailed look at an h-index, click on the author’s name to go to their profile. Look under the “Metrics Overview” column to the left and click on “View h-graph."

Google Scholar

On Google Scholar you can search by topic or author name. After searching, click on the author of interest’s name to view their profile. The righthand column will include their h-index.

Why do h-indexes matter?

H-indexes are now a common part of the process of evaluating job applicants for academic positions and for helping to inform tenure-and-promotion committees considering a colleague's research portfolio and that person's impact on their field. The h-index is also used to evaluate applicants for research grants. Part of the appeal of this metric is that it combines quantity and impact into a single value that can be directly compared across researchers within a discipline.

As with all metrics, however, there are limitations to the h-index as an indicator of excellence:

• Databases may have different results depending on their subject coverage and on which journals they index.
  • When comparing h-indexes for the same author across sites, favor the database with the largest number of publications.
• Like all metrics based on citation counts, the h-index can be manipulated through self-citations.
• The h-index does not account for the number or order of authors of a paper.
  • No distinction is made between a first author and coauthor. In other words, being the first author is not weighted more heavily.
• The h-index does not account for any variance in the typical number of citations between different fields.
  • It can be difficult, for example, to compare an h-index of a scientist to that of a social scientist or a humanist or even to compare, say, a chemist's score with a clinician's.
• The h-index does not account for how long the researcher has been working in the field.
  • Early-career researchers are put at a disadvantage by a metric that does not recognize that it takes considerable time both to publish and to garner citations.

What is the g-index?

In response to the popularity of the h-index, the g-index was introduced in 2006 by Leo Egghe. It is also an author-level impact metric, but it differs from the h-index in a few key respects.  

• The g-index adds more weight to an author’s highly cited articles. Whereas the h-index evaluates all articles equally
• The h-index tends to put early-career researchers at a disadvantage since they have not had as much time to publish as many articles as their more experienced peers 

To calculate your metrics, you can download the Publish or Perish software.  

Reference 

Harzing, A.W. (2007) Publish or Perish, available from https://harzing.com/resources/publish-or-perish