Remarkable growth of open access in the biomedical fi eld: analysis of PubMed articles from 2006 to 2010. PLoS ONE, 8(5): e60925. http://dx.doi. org/10.1371/journal.pone.0060925

Introduction: This study clarifies the trends observed in open access (OA) in the biomedical field between 2006 and 2010, and explores the possible explanations for the differences in OA rates revealed in recent surveys. Methods: The study consists of a main survey and two supplementary surveys. In the main survey, a manual Google search was performed to investigate whether full-text versions of articles from PubMed were freely available. Target samples were articles published in 2005, 2007, and 2009; the searches were performed a year after publication in 2006, 2008, and 2010