Measuring open access publications: a novel normalized open access indicator

The issue of open access (OA) to scientific publications is attracting growing interest within the scientific community and among policy makers. Open access indicators are being calculated. In its 2019 ranking, the ''Centre for Science and Technology Studies'' (CWTS) provides the number and the share of OA publications per institution. This gives an idea of the degree of openness of institutions. However, not taking into account the disciplinary specificities and the specialization of institutions makes comparisons based on the shares of OA publications biased. We show that OA publishing practices vary considerably according to discipline. As a result, we propose two methods to normalize OA share; by WoS subject categories and by disciplines. Normalized Open Access Indicator (NOAI) corrects for disciplinary composition and allows a better comparability of institutions or countries.