Measuring Citation Advantages of Open Accessibility

Over the past decade, a good number of studies have attempted to demonstrate that open access journal articles have higher citation rates than traditionally published ones. These open access articles are either published in open access journals or are made publicly available through open access repositories. More methodologically sound studies, however, are needed to pinpoint more exactly the impact, if any, of open accessibility on citation rates and to look at the issue of impact (or non-impact) more closely. For instance, of those journal articles that have been made openly accessible, about what percent of them benefit from open online availability? What percent of them do not?