(Just to remind you all - I'm away on holiday and I've pre-scheduled the publication of several posts from my old blog at blogspot. This next entry was one that I got a lot of 'tsks, tsks" for - it was intrended tio be a tad toungue & cheek. Incidentally the values of the various h-indexes listed here must have gone up.)

About a month ago I had a conversation with my thesis advisor about the h-index. It is a new method, proposed by Jorge E. Hirsch of UCSD to quantitatively measure a scientist's influence. His proposal was published in PNAS and Nature had a little report on it. Here's a publically available link to the paper (for those who don't have institutional access to PNAS).

The Abstract from the original PNAS paper:

I propose the index h, defined as the number of papers with citation number is [equal or greater than] h, as a useful index to characterize the scientific output of a researcher.

And here is the rationale from the paper:

Why would you try to quantitatively measure a scientist's influence? For the few scientists who earn a Nobel prize, the impact and relevance of their research is unquestionable. Among the rest of us, how does one quantify the cumulative impact and relevance of an individual's scientific research output? In a world of limited resources, such quantification (even if potentially distasteful) is often needed for evaluation and comparison purposes (e.g., for university faculty recruitment and advancement, award of grants, etc.).

So what is my h-index? To find out log into Thomson Scientific's ISI Web of knowledge, find all your papers and sort them based on citations. Scroll down the list until your paper rank is equal or greater than the citations for that paper. In my puny grad-student/postdoc career, I've only published 9 peer-reviewed papers. What follows is a bar graph of the number of times each paper was cited (citation number), and the paper rank where rank=citations, is paper #8.

Benefits of the h-index:
- It is quantitative.
- It takes into account not just the number of publications or how well a couple of publications are cited, but the QUANTITY of well cited publications.
- Older, well established professors will have accumulated many citations for initial work that is still relevant. Thus h-index goes up with time.
- As you increase your h-index number, it becomes harder to increase it further. Take my h-index: all i need to get to h-index=9 is to publish another paper and hope that it gets cited at least 9 times (and that my current #8 gets cited an extra time). So right now my h-index will roughly grow with the number of publications. Eventually as my h-index grows (to say 50), each new paper has to be cited at least as many times (in this example, 51 citations) to boost my h-index.

Problems:
- Self citations. Although this could easily be eliminated.
- Papers which are wrong. This is not so bad. If you are influential, by definition, people will have to confront and address your "bad data" and explain why it is wrong.
- Cross field comparison. Currently biologists have much higher h-indexes than physicists, simply because there are more scientists who study biology (and thus more individuals who can cite you). Even within biology, it looks like researchers studying signal transduction and oncogenes get a boost to their h-index.

Some h-indexes for notable biologists:

Francis Crick: 53
James Watson: 43
Sydney Brenner: 92
Keith Porter: 70

Some people in our vicinity ...

Marc Kirschner: 90
Tim Mitchison: 59
Tom Rapoport: 60
John Blenis: 64
Joan Brugge: 67
Tom Maniatis: 115
Lew Cantley: 97
Steve Harrison: 74
Jack Szostak: 63

other big guys ...

Gunter Blobel: 120
James Rothman: 92
Randy Schekman: 76
Ian Mattaj: 65
Rudolf Jaenisch: 96
Elaine Fuchs: 93
Richard Hynes: 94
Michael Sheetz: 65
Ron Vale: 56
Bert Vogelstein: 143
Bob Weinberg: 113
Susan Lindquist: 74
Harold Varmus: 103
Michael Bishop: 112
Phil Sharp: 115
Joan Steitz: 91
Tom Steitz: 85
Thomas Cech: 82
Alexander Varshavsky: 62
Eric Kandel: 117
Richard Axel: 80
Paul Nurse: 90
Lee Hartwell: 61

One problem with these lists ... we did the searches on ISI, but could not account for papers where the middle initial was omited so the true values for some researchers may be slightly higher ...

OK I've wasted enough time. I'll end with this quote from Hirsch's PNAS paper:

In summary, I have proposed an easily computable index, h, which gives an estimate of the importance, significance, and broad impact of a scientist's cumulative research contributions. I suggest that this index may provide a useful yardstick with which to compare, in an unbiased way, different individuals competing for the same resource when an important evaluation criterion is scientific achievement.

But of course this is all bxxl sxxt ...

{Update 1/28/06}

Acme Scientist informs me that Michael Behe's h-index is 15 ... interesting. Someone should compile the h-index of all these so-called experts ...

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In general, I despise the infiltration of beancounters into the scientific process who try to put a metric on everything that should be evaluated subjectively (like the contribution of my one paper vs. five turds from a competitor). However, I do like the h-index concept, even with some of the caveats you describe.

I also see two additional weaknesses. First, the h-index doesn't address an author's capacity for independent thought. You can be in the middle of 50 great papers with someone like Vogelstein and have an h-index of 50, but how independent are you really?

Second, there should also be some consideration of the h-index in the context of total papers published. Someone early in their career like you is doing pretty well to already have an h-index of 8. A lot of my most recent papers have yet to get more than a couple citations, meaning that they won't boost my h-index for quite some time even though I think they are some of my better work (I'll have to let you know my h-index later; under my real name, of course). But there may be people with an h-index of 50 who have published 60 papers in their career while another investigator with an h-index of 50 might have published 400 papers. Who do you think is the higher-impact scientist?

sounds a little like how google ranks pages. Citations from other scientists are like links from other web pages. More connections between papers/web pages equals more influence/higher page rank, right?

Couldn't resist: of my 14 papers, WoS knows about 13; they range from 0 citations to 21, and the 8-th ranked paper has 8 citations, so my h-index is 8.

Which brings up yet another weakness of the system: you have three strong papers with >50 citations and a total of around 300 citations, whereas my best is 21 and my total is 114. This, despite most of my papers being in HIV biology, a very active field. We have the same h-index, but your work has clearly had the higher impact.

Further, I dislike relying on the proprietary and expensive Thomson ISI. I wonder whether there is not a Google Scholar hack which would provide an alternative, freely available measure?

The h-index has both advantages and drawbacks. See the wiki page for a rather balanced view. Also see this paper (PDF) on the dangers of relying too much on the h-index.

I think h-index is very simple, but very attractive. In my opinion, it should be thougt that h-index reflects peer review, and peer review reflects resarch quality and quantity for journals, researchers, scientifics topics.

By ORBAY Metin-TURKEY (not verified) on 13 Apr 2007 #permalink

Better h-index

After h-index is calculated multiply it by the average number of citation of the papers contributing to h-index, and than take square root. This gives area based(A-index) of the h-index citation field. This removes problem that h-index of N can not distinguish is it N-times N-citations (the weakest possible case) or N-times of citations that are much larger of N. For instance h-index of 5 one can get by citations: 5 5 5 5 5, but also by citations: 50 5 5 5 5. A-index in this two cases is 5 and 8.4 respectively. Such an index will put science genius (milestone discovery) back to the top.

h-index of my publication

By daoud ali (not verified) on 26 Dec 2010 #permalink

Can't resist: I have 15 papers and the least cited has been cited 78 times. What is my h index?

I want to calculate my h index; i am in the field of Medicine

By Francois Berthoux (not verified) on 21 Nov 2011 #permalink

I want to calculate my h index; i am in the field of Medicine

By Francois Berthoux (not verified) on 21 Nov 2011 #permalink

Je veux calculer mon h index

By Abdelhakim mou… (not verified) on 22 Jan 2012 #permalink

You can calculate an approximate version of your H-index, based on Google Scholar, using the free program called Publish or Perish. http://www.harzing.com/pop.htm
And by the way, MJ Behe h-index is around 16... not bad. But he has been publishing on biochemistry since the 70s, some articles with significant citations had nothing to do with his positions on evolution and are from the early 90s. And lately he got a lot of citations (by criticisms) to his book or to the articles where his most controversial opinions are expressed. Thus, contradictorily, his h-index is somehow boosted by the contradictors to his arguments, and not mainly due to the positive scientific impact of his work.