Vanity Index IIPosted on July 26th, 2009 No comments
I missed a couple of things in my previous post on the h-index and citations.
- Michael Nielsen points out that the h-index is essentially redundant, because for most scientists it is nearly equal to half the square root of their total citations. So the h-index doesn’t carry any more information that the total number of citations.
- The total number of citations greatly depends on the field of research. Medicine and related subjects get huge citations, mathematics very few.
- The same problem affects journal impact factors — medical and bio-technological journals have high impact factors in the 20’s and 30’s, while math journals are languish under 2.
It seems like a sensible conjecture that impact factor of a journal increases with the total number of citations per year in the field. It may be the same function with different constant prefactors for different journals.
Total number of citations per year in a field should be a power function (n^2 seems likely) of the total number of papers written in the field per year.
Total number of papers should be directly proportional to the total number of researchers in the field. The proportionality constant may be different for different fields.
So the impact factor of a journal should be a function of the number of researchers in the field, multiplied by some contant factor depending on the journal. The function should be the same function for all fields.
On the other hand, if you want to have a high h-index, join a club where everyone writes a few (or several) papers every year, and cites everyone else in the club.
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