Abstract Open Access has changed how research is published and discovered. Studies generally report that OA articles are cited and mentioned more often than non‐OA, describing an open access advantage (OAA). The mechanisms causing the OAA are under‐investigated: this research analyzes citation and altmetrics post‐publication, reporting on the development of OAAs over time. A set of journal articles ( N = 44.4 M) is analyzed using seven metrics (citations from journal articles and six altmetrics), using a longitudinal methodology. These data are presented as a ratio of OA:non‐OA. OAAs are confirmed for many metrics: early advantages are strong for citation and policy metrics, moderate for news and blogs, and mostly absent for patent citations. Many OAAs are sustained in the years post‐publication, although citation OAAs, which typically drop in the year after publication, grow strongly in the following years. OAAs do not generally disappear over time, with the exception of policy citations. Most OAAs appear shortly after publication, and although some develop over time, they are generally sustained in subsequent years. The evidence favors an explanation associated with early activity; other explanations are required to understand subsequent changes in OAAs. There are significant implications for funders, researchers, and publishers.
Michael Taylor (Thu,) studied this question.