I received a kind email from Elsevier this morning, updating me on the amazing improvement in 2011 Impact Factor (versus 2010) for several journals in their stable of "Behavioral & Cognitive Neuroscience Journals". There are three funny bits here, first that the style was:
2010 Impact Factor WAS 2.838, 2011 Impact Factor NOW 3.174
You have to admit the all-caps is a crack up. Second, THREE decimal places! Dudes, this shit is totally precise and that means....sciencey.
As you know, however, DearReader, I have a rather unhealthy interest in the hilariousity of the Impact Factor and I was thinking about the more important issue here.
Is this a significant difference? Who gives a hoot if the IF goes up by 0.336? Is this in any way meaningful?
I suspect the number of available citations is ever on the increase. The business of science is ever expanding, the pressure to publish relentless and the introduction of new journals continues. This means that IFs will be on some baseline level of background increase over time. This is borne out, I will note, by my completely unscientific tracking of journals most closely related to my interests over the past *cough*cough* years *cough*cough*. They all seem to have gradually inched up a few decimal points year in, year out.
For the 0.336 increase, let us do a little seat of the pants. Let's say a journal with 20 articles per issue, 12 issue per year....480 items over the 2 year tracking interval for calculating IF. Round it to 160 extra citations*. If only 17% of the articles got two more citations, this would account for it. If a mere 3% of articles turned out to be AMAZING for the sub-sub-sub field and won an extra 10 citations each....this would account for the change.
For one thing, I can now see why editors would be willing to try the "Cite us a few more times" gambit with authors in the review stage. It doesn't take many intimidated authors throwing in 4-5 more citations of recent work from the journal in question to move a third of an impact factor.
Heck, just one solo operator author could probably make a notable impact over two years. If I put everything we submit into a single journal over two years time, and did my level best to make sure to cite everything plausibly relevant from that journal, I could generate 40 extra citations in two year easily. Probably without anyone so much as noticing what I was up to!
The fact that the vast majority of society rank journals that I follow fail to experience dramatic IF gains suggests that nobody is trying to game the system like this and that seemingly universal increases are a reflection of overall trends for total number of publications. But it does make you wonder about those few journals that managed to gain** a subjective rank over a few years time, say from the 2-4 to the 6-8 range and just how they pulled it off.
This tool permits you to search some citation trends by journal.
*Yes, I realize the overlap year for adjacent annual IFs. For our thought exercise, imagine it is non-overlapping years if this bothers you.
**My hypothesis is that an editorial team would only have to pull shenanigans for 2-4 years and after that the IF would be self-sustaining.