Sunday, June 22, 2008

(What is) "hirsch index" and "impact factor"? and is it fair?

Better metrics for an individual's value on Nature's network got me thinking. How fair is to evaluate an academic with some numbers that may or may not reflect the individual's quality?

Perhaps there's no better way to assess the "impact" of a research or the author other than counting the number of articles that cite it. And the journals. How do we tell Science or Nature is better than all others?

Instead of going into existential criticism of academic affairs I should explain impact factor and hirsch index really briefly and leave the judgment to you:

Impact factor (IF) = Number of total citations / Number of articles

We can calculate IF for a journal or a professor. But when calculating for a professor you need to exclude his/her own papers that cite the previous ones.

The leading journals in materials and nano science (according to IF) are
1. Science and Nature ~ 30
2. Nature Materials ~ 19
3. Nano Letters ~ 10
4. Angewandte ~ 10
5. Advanced Materials ~ 8
6. JACS ~ 8

Hirsch index is named after its inventor Dr. Jorge Hirsch, a UCSD professor of Physics. The idea is -roughly- getting a median of all highly cited papers. For example if you have 10 papers and 4 of them has 4 or more citations then your h-index is 4. For the number of citations you need to look in Web of Science, SciFinder and Google Scholar.

In a sense, hirsch index provides more fair evaluation then impact factor but relying on it might be dangerous, as it's suggested for tenure evaluations and other critical investigations:

"Based on his calculations, Hirsch suggests that, for physicists, a value for h of about 12 might be a useful guideline for tenure decisions at major research universities. A value of about 18 could mean a full professorship, 15–20 could mean a fellowship in the American Physical Society, and 45 or higher could mean membership in the National Academy of Sciences."

The last thing an academician wants is to be measured by numbers.

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