Thomson Reuters has released its 2009 Journal Citation Report, cataloging journals' impact factors, and shuffling in the top few spots have some analysts scratching their heads.

Specifically, the publication with second highest impact factor in the "science" category is Acta Crystallographica - Section A, knocking none other than the New England Journal of Medicine from the runner's up position. This title's impact factor rocketed up to 49.926 this year, more than 20-fold higher than last year. 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.)

"Without another, similarly important article in 2010, Acta Crystallographica - Section A is likely to return in 2011 to its prior Journal Impact Factor of between 1.5 and 2.5," wrote Marie McVeigh, director of Journal Citation Reports and bibliometric policy at Thomson Reuters, in a discussion forum on the company's website.

Number one stayed the same from last year's to this year's list -- CA: A Cancer Journal for Clinicians

Other surprises in this year's impact factor roundup include:

- PLoS ONE debuted in the Journal Citation Report for the first time with a respectable impact factor of 4.351. This score puts the open access journal in the top 25th percentile for biology publications. But might this sudden success be more of a bane than a boon to PLoS ONE, blogger Philip Davis asks. It may turn out that accepting 70 percent of the manuscripts submitted to your journal gets a bit trickier when you're flooded with papers.

- The Cell family of journals made an impressive showing in this year's report. Cell Stem Cell came in with a 23.563 impact factor, a 40 percent growth over last year's rating. Cell Host and Microbe's impact factor also grew, coming in 75 percent higher than last year, at 13.021. Cell, however, was knocked from the top ten.

- Nature Genetics made it into the top ten, with an impact factor of 34.284.

- 1055 new titles were ranked, and more than 700 of those publications were added as part of Thomson Reuters' new "Regional Content Expansion."

- More than 4700 titles showed an increase over their 2008 impact factors.

(Editor's note: 21st June - Marie McVeigh was incorrectly referred to as a Thomson Reuters blogger in the original version of this story. The mistake has been corrected above. The Scientist regrets the error.)


Related stories:

Down with Reviews
[April 2010]

Citation amnesia: The results
[25th June 2009]

New impact metric
[19th January 2009]