One of the benefits of Open Access (OA) is the increased audience and potential for greater citation, and many studies have been done to examine this 'citation advantage' (where OA articles receive more citations than equivalent subscription articles). A recent publication by Ben Wagner reviews the literature and weighs the evidence, finding the majority of studies show a significant OA citation advantage. Open Access citation advantage: an annotated bibliography provides a useful summary of the way studies were carried out including scope, subject area and main conclusions. The typical advantage is 25%-250%.
A small number of studies found no advantage, though most of these focus on specific subject areas. No studies were found to show any citation disadvantage for OA.