Molecular Biology and Evolution impact factor: the MEGA effect

(update March 2015 here)

So yesterday come out the new impact factors for journals, and while all serious people agree most of the year that they don’t mean much, when they come out and your favorite journal went up you notice.

Molecular Biology and Evolution (MBE) is the main journal of the molecular evolution community. It’s impact factor just went up from 5.5 to 10.5. Last time there was such a jump, it was due to citations to a paper describing the updated MEGA software, so I suspected something of the sort. And indeed, here are the top cited papers in MBE in 2011-2012:

Title: MEGA5: Molecular Evolutionary Genetics Analysis Using Maximum Likelihood, Evolutionary Distance, and Maximum Parsimony Methods
Author(s): Tamura, Koichiro; Peterson, Daniel; Peterson, Nicholas; et al.
Source: MOLECULAR BIOLOGY AND EVOLUTION Volume: 28 Issue: 10 Pages: 2731-2739 DOI: 10.1093/molbev/msr121 Published: OCT 2011
Times Cited: 4,135 (from All Databases)

Title: Bayesian Phylogenetics with BEAUti and the BEAST 1.7
Author(s): Drummond, Alexei J.; Suchard, Marc A.; Xie, Dong; et al.
Source: MOLECULAR BIOLOGY AND EVOLUTION Volume: 29 Issue: 8 Pages: 1969-1973 DOI: 10.1093/molbev/mss075 Published: AUG 2012
Times Cited: 64 (from All Databases)

Title: Statistical Properties of the Branch-Site Test of Positive Selection
Author(s): Yang, Ziheng; dos Reis, Mario
Source: MOLECULAR BIOLOGY AND EVOLUTION Volume: 28 Issue: 3 Pages: 1217-1228 DOI: 10.1093/molbev/msq303 Published: MAR 2011
Times Cited: 33 (from All Databases)

Notice anything? It goes on down from there.

Confirmation: the previous MEGA paper in MBE was published in 2007. Here is the graph of citations to MBE from ISI over the years:


Clicking will take you to ISI. If you don’t have a subscription, tough luck, that’s what happens when we let a corporation rank our journals.

Let’s try to recalculate the impact factor of MBE without MEGA for the last two years. According to ISI, these are the numbers:

  • Cites in 2012 to items published in: 2011 = 3807; 2010 = 1939
  • Number of items published in: 2011 = 297; 2010 = 258

The MEGA5 paper was cited 2473 times in 2012, so updating the numbers, we get:

  • 3807-2473+1939 = 3273 cites
  • 297-1+258 = 554 items
  • thus 3273/554 = 5.9 impact factor.

Who would have thought? It didn’t change!

Amusingly, there was an even more striking jump of impact factor of Briefings in Bioinformatics a few years ago, for which I don’t have time to look up the numbers, which was also entirely due to a MEGA update.

Anyway, have fun checking your new impact factors. Don’t forget the three decimal points. For MBE, it’s 10.353.

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