Evaluating Open Access Advantages for Citations and Altmetrics (2011-21): A Dynamic and Evolving Relationship

Differences between the impacts of Open Access (OA) and non-OA research have been observed over a wide range of citation and altmetric indicators, usually finding an Open Access Advantage (OAA) within specific fields. However, science-wide analyses covering multiple years, indicators and disciplines are lacking. Using citation counts and six altmetrics for 38.7M articles published 2011-21, we compare OA and non-OA papers. The results show that there is no universal OAA across all disciplines or impact indicators: the OAA for citations tends to be lower for more papers, whereas the OAAs for news, blogs and Twitter are consistent across years and unrelated to volume of OA publications, whereas the OAAs for Wikipedia, patents and policy citations are more complex. These results support different hypotheses for different subjects and indicators. The evidence is consistent with OA accelerating research impact in the Medical & Health Sciences, Life Sciences and the Humanities; that increased visibility or discoverability is a factor in promoting the translation of research into socio-economic impact; and that OA is a factor in growing online engagement with research in some disciplines. OAAs are therefore complex, dynamic, multi-factorial and require considerable analysis to understand.