Abstract
Despite growing interest in Open Access (OA) to scholarly literature, there is an unmet need for large-scale, up-to-date, and reproducible studies assessing the prevalence and characteristics of OA. We address this need using oaDOI, an open online service that determines OA status for 67 million articles. We use three samples, each of 100,000 articles, to investigate OA in three populations: (1) all journal articles assigned a Crossref DOI, (2) recent journal articles indexed in Web of Science, and (3) articles viewed by users of Unpaywall, an open-source browser extension that lets users find OA articles using oaDOI. We estimate that at least 28% of the scholarly literature is OA (19M in total) and that this proportion is growing, driven particularly by growth in Gold and Hybrid. The most recent year analyzed (2015) also has the highest percentage of OA (45%). Because of this growth, and the fact that readers disproportionately access newer articles, we find that Unpaywall users encounter OA quite frequently: 47% of articles they view are OA. Notably, the most common mechanism for OA is not Gold, Green, or Hybrid OA, but rather an under-discussed category we dub Bronze: articles made free-to-read on the publisher website, without an explicit Open license. We also examine the citation impact of OA articles, corroborating the so-called open-access citation advantage: accounting for age and discipline, OA articles receive 18% more citations than average, an effect driven primarily by Green and Hybrid OA. We encourage further research using the free oaDOI service, as a way to inform OA policy and practice.
Highlights
The movement to provide open access (OA) to all research literature is over fifteen years old
People reading the literature using the Unpaywall browser extension encounter a significantly higher proportion of OA: we found that 47.0% of the Unpaywall-accessed sample is open access
Using data from one of these tools, this paper addresses two broad research questions: what percent of the literature is OA and how does it vary by type of OA, and what is the mean scholarly impact of papers diffused through this form
Summary
The movement to provide open access (OA) to all research literature is over fifteen years old. Funding institutions are increasingly mandating OA publishing for grantees. In addition to the US National Institutes of Health, which mandated OA in 2008 (https://publicaccess.nih.gov/index.htm), the Bill and Melinda Gates Foundation (http://www.gatesfoundation.org/How-WeWork/General-Information/Open-Access-Policy), the European Commission (http:// ec.europa.eu/research/participants/data/ref/h2020/grants_manual/hi/oa_pilot/h2020-hioa-pilot-guide_en.pdf), the US National Science Foundation (https://www.nsf.gov/pubs/ 2015/nsf15052/nsf15052.pdf), and the Wellcome Trust (https://wellcome.ac.uk/pressrelease/wellcome-trust-strengthens-its-open-access-policy), among others, have made OA diffusion mandatory for grantees. Several tools have sprung up to build value atop the growing OA corpus. These include discovery platforms like ScienceOpen and 1Science, and browser-based extensions like the Open Access Button, Canary Haz, and Unpaywall. As the toll-access status quo becomes increasingly unaffordable, institutions are looking to OA as part of their ‘‘Plan B’’ to maintain access to essential literature (Antelman, 2017)
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