Author-choice open access publishing in the biological and medical literature: a citation analysis, Philip M Davis, Journal of the American Society for Information Science and Technology, 2009; 60(1), 3-8 [PDF]. Abstract:
In this article, we analyze the citations to articles published in 11 biological and medical journals from 2003 to 2007 that employ author-choice open-access models. Controlling for known explanatory predictors of citations, only 2 of the 11 journals show positive and significant open-access effects. Analyzing all journals together, we report a small but significant increase in article citations of 17%. In addition, there is strong evidence to suggest that the open-access advantage is declining by about 7% per year, from 32% in 2004 to 11% in 2007.
Found via: Citation advantage as Holy Grail by Nick Sheppard, Repository News, January 6, 2009.