Have you been asked for your H-index recently? Are you clear on what the metric says about you? Karen Clews and guest blogger Vicky Wallace look at how the metric has developed and how you can use it responsibly
Developed by Hirsch in 2005 to help evaluate researchers in theoretical physics, the H-index gives a researcher a number or 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.
The measure has certainly gained a lot of followers over the years, and announcements of high profile appointments within the sector usually include a comment about their incredibly impressive H-index. H-indices can be easily calculated in various bibliometric tools out there, including Google Scholar, Web of Science and Scopus making it 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.
There has been a lot written on this topic (a list of which we will include at the end of this post), but to sum up, the top concerns raised are that:
- As it is a measure which can only go up over time it favours authors at the middle or end of their careers
- 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 feign language are especially badly represented in the bigger databases.
- The index takes no account of the number or authors or the positioning of the author in the paper.
- There is not easy way to know what a “good” H-index is in a certain discipline, and no way to compare across disciplines.
There is a growing movement to start to remove the H-index from official processes such as recruitment, especially as there has been some much work done to develop new field weighted metrics which go a long way to solve the issues of the H-index. Despite the issues, the h index is being taken seriously by many people and you may be asked for your h index as part of a grant application, or elsewhere.
So, if you have to provide a H-index, here are our top 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. Ensure that all your papers are properly attributed and that no one else’s pages have been attached to you.
- Show your working out! It’s ok to check your h index on each of the databases to see which database gives you the highest score, but you must make sure you clearly cite where you have calculated your H-index from. Google Scholar has a reputation for counting more citations than databases such as Scopus, so it is important to ensure that people are aware of 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 indexes across disciplines and different career stages. If yours seems low, look deeper at your own score – is it a fair representation of your research, or would it be worth adding in an alternative score?
- Include other information where possible – Is there some contextual information that you can add to your application, e.g. a paper that has been very highly cited which is not adequately represented by your H-index? Remember a key to being responsible with research metrics is to use a basket of metrics – don’t just rely on one measure to encapsulate your entire research career.
- Be ready to challenge the use of the h index and understand the issues around it. If you feel that this is not the measure you want to be measured by, say so! There are other metrics out there such as the Field Weighted Citation Impact or average citations per paper, which can, in combination, demonstrate the strength and quality of your research in a much better, more responsible, way.
Read more about the H-index:
- The Conversation: what is an H-index and how is it calculated? – http://theconversation.com/explainer-what-is-an-h-index-and-how-is-it-calculated-41162
- PLOS Biologue: Why I love the H-index – http://blogs.plos.org/biologue/2012/10/19/why-i-love-the-h-index/
- Impact story blog – Four great reasons to stop caring so much about the H-index – http://blog.impactstory.org/four-great-reasons-to-stop-caring-so-much-about-the-h-index/
- How does a scientis’s H-index change over time? – https://jeffollerton.wordpress.com/2015/05/10/how-does-a-scientists-h-index-change-over-time/
- The Guardian: The h-index, or the academic equivalent of the stag’s antlers – https://www.theguardian.com/commentisfree/2012/jan/06/bad-science-h-index
Variations on a theme
Find out more about various alternatives to the H-index that have been developed over the years:
These alternatives have been developed to address some of the problems highlighted in this post, but have not become as widely used, e.g:
G index – giving more weight to highly cited papers, it is defined “the highest number g of papers that together received g2 or more citations
i10 index – again giving more weight to highly cited papers, i10 index is the number of publications with at least 10 citations. It was introduced in July 2011 by Google, and can be accessed by setting up a Google Scholar Citations Profile.
M index/m quotient – also devised by Hirsch, this score adjusts for the bias towards middle or late career researchers by dividing the h-index by the number of years since a scientist’s first publication.
Contemporary H index – Devised by Sidiropoulos, Katsaros, and Manolopoulos, and available in Publish or Perish, this score weights recent citations more heavily:
- For an article published in the current year, each citation is counted 4 times
- For an article published 4 years ago, each citation is counted once
- For an article published 6 years ago, each citation is counted 4/6 times, etc
These are just some of a wide range of variants on the h index.