Government Social Research
16 May 2006: Open access brings more citations: analysis of PNAS articles suggests that open access papers are cited more heavily than subscription-based articles - article in The Scientist
Open access articles were cited more heavily both four to 10 and 10 to 16 months after publication, both when the author considered only raw data and when he also accounted for such potential "confounders" as number of authors, past productivity, country of corresponding author, and submission track. For instance, after adjusting for confounders, open access articles were almost three times more likely than non-open access articles be cited at least once 10 to 16 months after publication. Self-archiving, in which authors post a paper for free on the Internet, also appeared to increase citations. There was "a clear relationship between the level of openness and the citation levels."
The author told The Scientist he plans to continue monitoring his
dataset at six-month intervals, noting that his latest
data suggest the open access advantage continues to widen at 16 to
22 months post-publication.