This one’s a bit of a head-scratcher. Thomson-Reuters just released its 2009 Journal Citation Report–essentially a comprehensive ranking of scientific journals by their impact factor (IF). The odd part, as reported by Bob Grant in The Scientist, is that the journal with the second-highest IF is Acta Crystallographica – Section A–ahead of heavyweights like the New England Journal of Medicine. For perspective, the same journal had an IF of 2.051 in 2008. The reason for the jump?
A single article published in a 2008 issue of the journal seems to be responsible for the meteoric rise in the Acta Crystallographica – Section A‘s impact factor. “A short history of SHELX,” by University of Göttingen crystallographer George Sheldrick, which reviewed the development of the computer system SHELX, has been cited more than 6,600 times, according to ISI. This paper includes a sentence that essentially instructs readers to cite the paper they’re reading — “This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.” (Note: This may be a good way to boost your citations.)
Setting aside the good career advice (and yes, I’ve made a mental note to include the phrase “this paper could serve as a general literature citation…” in my next paper), it’s perplexing that Thomson-Reuters didn’t downweight Acta Crystallographica‘s IF considerably given the obvious outlier. There’s no question they would have noticed that the second-ranked journal was only there in virtue of one article, so I’m curious what the thought process was. Perhaps the deliberation went something like this:
Thomson-Reuters statistician A: We need to take it out! We can’t have a journal with an impact factor of 2 last year beat out the NEJM!
Thomson-Reuters statistician B: But if we take it out, it’ll look like we tampered with the IF!
TRS-A: But we already tamper with the IF! No one knows how we come up with these numbers! Sometimes we can’t even replicate our own results ourselves! And anyway, it’s really not a big deal if we just leave the article in; scientists know better than to think Acta Crystallographica is the second most influential science journal on the planet. They’ll figure it out.
TRS-B: But that’s like asking them to just disregard our numbers! If you’re supposed to ignore the impact factor in cases where it contradicts your perception of journal quality, what’s the point of having an impact factor at all?
TRS-A: Beats me.