Developed by Hirsch in 2005, the h-index gives a researcher a score which attempts to demonstrate both the productivity and citation impact of their publications. A researcher has index h if h of his/her Np papers have at least h citations each, and the other (Np−h) papers have no more than h citations each. In other words, a researcher with a h-index of 10 has had 10 of their papers cited at least 10 times. h-indices can be calculated using various tools, including Google Scholar, Web of Science and Scopus.
The measure has gained many followers over the years as it is a quick and accessible metric for researchers to use to demonstrate their research power. However, as the popularity of the measure has grown, so too have the concerns about its flaws and perceived irresponsible representation of citation impact.
- It favours authors at the middle or end of their careers, as it is a measure which can only go up over time.
- It favours authors in disciplines with fast publication rates, and with cultures of extensive referencing and multiple authorship.
- It ignores small numbers of important articles. Highly cited articles are likely to be the most important, but their importance is reduced as the score increases only as citations and publications accumulate.
- Incomplete coverage by citation indexes makes the calculation of a researcher’s h-index vary, sometimes wildly, from one bibliometric database to another. Coverage of books and chapters, outputs in a foreign language are especially badly represented in some databases.
- The index takes no account of the number of authors, or the positioning of the author in the paper.
- There is not an easy way to know what a “good” h-index is in a certain discipline, and no way to compare across disciplines.
Whilst variations on the h-index have been developed to address some of these problems, e.g. g-index, i10 index, m-index, contemporary h-index, these are not as widely used.
Because of the issues, there is a growing movement to remove the h-index from official processes. The University established the Responsible and Fair Approaches to Research Assessment (RFARA) Task and Finish Group to explore how best to integrate responsible and fair metrics, principles and practices into our research environment. Funders are engaging with this too, with UKRI issuing the following guidance: "The content of a paper is more important than publication metrics, or the identity of the journal, in which it was published, especially for early-stage investigators. Therefore, you should not use journal impact factor (or any hierarchy of journals), conference rankings and metrics such as the H-index or i10-index when assessing UKRI grants."
How to use the h-index
If you are asked to provide your h-index, here are some tips on how to do it responsibly:
- Take responsibility for your online identity. Ensure you have curated your online profile on at least the database you are going to use – Google Scholar, Scopus or Web of Science.
- Show your working out. You can check your h-index on each of the databases to see which gives you the highest score. Google Scholar has a reputation for counting more citations than Scopus and Web of Science, so state the source you used and the date it was calculated so that it can be replicated and/or defended if necessary.
- Know what good looks like. To get a feel for what is a “good” h-index in your field, check the h-index of a colleague in your discipline area who is at a similar career stage to yourself. Never compare h-indices across disciplines and different career stages.
- Include other information. Don’t just rely on one measure to encapsulate your entire research career. Include contextual information e.g. a paper that has been very highly cited which is not adequately represented by your h-index.
- Be ready to challenge the use of the h-index and understand the surrounding issues. If you feel that this is not the measure you want to be measured by, say so! There are other metrics such as the Field Weighted Citation Impact and Beamplots which can, in combination, demonstrate the strength and quality of your research in a more responsible way.
Finding your h-index
You can find your h-index on Web of Science, Scopus and Google Scholar.
On Web of Science, access your author profile by clicking to search 'Authors', completing the search form and clicking 'Search'. You may need to refine by subject category and organization, and to select one or more author record(s) from the results. The author profile gives a list of publications with the h-index and other scores in the 'Citation Network' box on the right of the page (you may need to scroll down a little to see it).
On Scopus, access your author profile by clicking on 'Authors', entering your author name, or ORCiD, and clicking 'Search'. Click on the correct author name, or if there is more than one, select them by ticking the boxes, then the 'request to merge authors' link at the top. The metrics overview can be seen on the left of the screen.
For Google Scholar, metrics are available in 2 ways. Google Scholar author profiles list metrics on the right of the screen.
If you do not wish to create a Google Scholar profile, or you are checking the metrics of another author, Harzing's Publish or Perish can be downloaded and then accessed from your Start menu. Within Publish or Perish, start by clicking on the button 'G Google Scholar', then type the author name into the author box and click on 'Lookup'. Papers with the highest number of cites will be displayed at the top –a blue h is displayed where these contribute to the h-index. You may need to do some editing to remove papers by other authors and duplicates where citations have been obtained from different data sources - to identify and merge these, and their citation counts, click on the Title column heading to sort by title, then drag and drop to merge items (unmerge items by right-clicking on the item and choosing 'Split').
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