As open access (OA) articles are freely available, the potential readership and impact is much greater than for articles where access to the full-text is limited to subscribers only. But does increasing the visibility of research result in more citations?

Studies suggesting that this Open Access Citation Advantage (OACA) exists have been challenged due to a number of unaddressed confounding factors, such as self-selection bias, where authors may preferentially choose higher-quality articles for OA. Furthermore, existing papers addressing the OACA have focused on specific disciplines, used small sample sizes or assessed articles that may not have been OA long enough to show a significant effect on citation rate.

Jim Ottaviani aimed to address some of these issues in  a new study published in PLOS one, which utilised the University of Michigan’s institutional repository service, Deep Blue. OA articles (n=3,850) were selected that previously were subscription only but had been made available in Deep Blue via blanket licensing agreements between the publisher and library, and therefore were not self-selected for OA by the author. These were compared with articles from the same journal which remained subscription only (n=89,895). The number of citations were recorded for the OA articles while access was open and closed and compared with articles that remained closed during the same time period. The study found that an OACA as high as 19% exists, and that better articles gain more from OA.

The author describes the limitations of the data including the fact that many articles were past their peak citation years and concludes by discussing the difficulties and current barriers to carrying out this type of research.

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Summary by Alice Wareham, PhD from Aspire Scientific