“Utility of primary scientific literature to environmental managers: an international case study on coral-dominated marine protected areas” (preprint, Nov 2017)…

“To assess accessibility of MPA science to decision-makers we conducted a literature search using the database SCOPUS … limiting our search to all ‘articles’ and ‘reviews’ published between 1 January 2009 and 31 December 2012. … only 43% of primary scientific articles and 50% of review papers relating to coral dominated MPAs [marine protected areas] were freely accessible to decision makers.”

Although keep in mind here that SCOPUS only has 29.18% coverage of the DOAJ Open Access titles, so is not likely to do well on many types of OA indexing test.