A taxonomy of articles in PubMed Central

Summary: "The total number of articles published in the 4-month interval (April 7 to August 7, 2008) and contributed to PMC was 23960. The four subtypes of articles in PMC, and their estimated proportions during this 4-month interval, are: 1) Author manuscripts that are publicly accessible (7346/23960=30.7%); 2) Articles that are embargoed (378/23960=1.6%); 3) Articles that are Libre OA (3635/23960=15.2%); 4) Other articles that are publicly accessible, via Gratis OA (12601/23960=52.5%). These proportions are probably not very different for the subset of NIH-supported articles, if it’s assumed that, during this 4-month interval, about 50-60% of the articles contributed to PMC were NIH-supported."