“In recent years, the level of availability has reached a tipping point, whereby at least half of the articles published become available in open access within 12 to 18 months of their publication….This report compares established commercial databases—namely, the Web of Science and Scopus—with a bibliographic database that has been produced with the goal of facilitating the retrieval of gold and green2 open access articles published in peer-reviewed journals. In addition to examining the strengths and limitations of large-scale measurement, this report performs a number of measures, particularly at the country and academic-field levels. It also examines the question of whether articles available in open access are more highly cited that those available strictly with a subscription….The evidence presented in this report shows that at least two-thirds of the articles published between 2011 and 2014 and having at least one U.S. author can be downloaded for free as of August 2016. In the case of Brazil, the proportion reaches 75%. More broadly, the vast majority of the large scholarly publishing countries have more than 50% of their articles published from 2010 to 2014 freely available for download in gold and/or green gratis open access. Examining the availability of articles by domains of scholarly activity shows that health sciences has the most articles available for free (at least 59% of the articles published in 2014 could be read for free in 2016), followed by the natural sciences (55%), applied sciences (47%), economic and social sciences (44%), and arts and humanities (24%)….Whereas current data suggests that gold OA is prevalent in health sciences, green dominates the natural sciences, applied sciences, and economic and social sciences. In the humanities, green and gold are more or less on the same level. …There is evidence that articles available in green OA are overall the most highly cited….”