  The implementation of policies promoting the adoption of an Open Science
culture must be accompanied by indicators that allow monitoring the penetration
of such policies and their potential effects on research publishing and sharing
practices. This study presents indicators of Open Access (OA) penetration at
the institutional level for universities worldwide. By combining data from Web
of Science, Unpaywall and the Leiden Ranking disambiguation of institutions, we
track OA coverage of universities' output for 963 institutions. This paper
presents the methodological challenges, conceptual discrepancies and
limitations and discusses further steps needed to move forward the discussion
on fostering Open Access and Open Science practices and policies.
