2010 ISI Impact Factors are now out

You can't ignore the fact that Impact Factors have had a huge effect on publishing trends and the choices authors make about where to publish. This is somewaht unfortunate - I now hear scientists talking in the corridors of universities, or worse, at conferences, about where they published their most recent paper, not what they are publishing on!

Regardless of how much weight you put on Impact Factors (see this damning review as evidence that some don't rate IFs at all), all new PhD students and Post-Docs have to play a game of publishing in (perceived) high impact journals if they are to get that next job.

So what are Impact Factors and how are they calculated?

In a given year, the impact factor of a journal is the average number of citations received per paper published in that journal during the two preceding years. For example, if a journal has an impact factor of 3 in 2009, then its papers published in 2007 and 2008 received 3 citations each on average. The 2009 impact factor of a journal would be calculated as follows:

A = the number of times articles published in 2007 and 2008 were cited by indexed journals during 2009

B = the total number of "citable items" published by that journal in 2007 and 2008. ("Citable items" are research papers; not editorials, book reviews or Letters-to-the-Editor)

2009 impact factor = A/B.

I've included the 2010 Impact Factors for journals in conservation and plant ecology (and compared their "performance" to their 2009 rating). The big winners were Ecology Letters, Trends in Ecology and Evolution and Frontiers in Ecology and the Environment. Interestingly, the IFs of most journals rose over the last year.

Applied Vegetation Science: 1.802 (2010) versus 1.349 (2009)
Austral Ecology: 1.820 versus 1.578
Australian Journal of Botany: 1.681 versus 1.868
Biodiversity and Conservation: 2.146 versus 2.066
Biological Conservation: 3.498 versus 3.167
Conservation Biology: 4.894 versus 4.666
Diversity and Distributions: 4.248 versus 4.224
Ecography: 4.417 versus 4.385
Ecological Applications: 4.276 versus 3.672
Ecology: 5.073 versus 4.411
Ecology Letters: 15.253 versus 10.318
Frontiers in Ecology and Environment: 8.820 versus 6.922
Functional Ecology: 4.645 versus 4.546
Global Change Biology: 6.346 versus 5.561
Global Ecology and Biogeography: 5.273 versus 5.913
Journal of Applied Ecology: 4.970 versus 4.197
Journal of Biogeography: 4.273 versus 4.087
Journal of Vegetation Science: 2.457 versus 2.376
Molecular Ecology: 6.457 versus 5.96
Nature: 36.101 versus 34.480
Oecologia: 3.517 versus 3.192
PNAS: 9.771 versus 9.432
Polar Biology: 1.445 versus 0.582
Science: 31.364 versus 29.747
Trends in Ecology and Evolution: 14.448 versus 11.564