Letter to the editor in Science

Science 17 July 2009:
Vol. 325. no. 5938, p. 266
DOI: 10.1126/science.325_266c

Letters
Open Access: The Sooner the Better
In the Brevia “Open access and global participation in science” (20 February, p. 1025), J. A. Evans and J. Reimer argue that a research article published online is only modestly (8%) more likely to be cited if it is freely available. This result would seem to cast doubt on one important argument in favor of free access—that it will increase the visibility of a paper to colleagues.

However, the 8% statistic that Evans and Reimer highlight is misleading. The authors’ supporting online material (figure S1C) clearly shows that the impact of free access on citations is heavily dependent on the age of the article at the time free access was provided. In particular, when articles were made freely available within 2 years of publication, their citations increased by almost 20%.

This far more dramatic effect is the one scientists and journals should consider when deciding when to provide free access. If this decision is to be made purely on the basis of citation impact, the upward trend of the curve in figure S1C argues strongly in favor of minimal delays.

Unfortunately, it is hard to tell exactly how short a delay the data support, because the underlying citation information is not provided. That the raw data for such a provocative paper is unavailable is an astonishing violation of the norms of science, and the explicitly stated publication policies of Science.

Michael Eisen1,* and Steven Salzberg2

* To whom correspondence should be addressed. E-mail: mbeisen@berkeley.edu

1 Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
2 Center for Bioinformatics and Computational Biology, Department of Computer Science, University of Maryland, MD 20742, USA.