This review aims to to be a resource for current knowledge on the impacts of Open Access by synthesizing important research in three major areas of impact: academic, economic and societal. While there is clearly much scope for additional research, several key trends are identified, including a broad citation advantage for researchers who publish openly, as well as additional benefits to the non-academic dissemination of their work. The economic case for Open Access is less well-understood, although it is clear that access to the research literature is key for innovative enterprises, and a range of governmental and non-governmental services. Furthermore, Open Access has the potential to save publishers and research funders considerable amounts of financial resources. The social case for Open Access is strong, in particular for advancing citizen science initiatives, and leveling the playing field for researchers in developing countries.
We contend that the current lack of financial transparency around scholarly communication is an obstacle to evidence-based policy-making – leaving researchers, decision-makers and institutions in the dark about the systemic implications of new financial models. We conclude that obtaining a more joined up picture of financial flows is vital as a means for researchers, institutions and others to understand and shape changes to the sociotechnical systems that underpin scholarly communication.