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. 2018 Feb 13:6:e4375.
doi: 10.7717/peerj.4375. eCollection 2018.

The state of OA: a large-scale analysis of the prevalence and impact of Open Access articles

Heather Piwowar #  1 , Jason Priem #  1 , Vincent Larivière  2   3 , Juan Pablo Alperin  4   5 , Lisa Matthias  6 , Bree Norlander  7   8 , Ashley Farley  7   8 , Jevin West  7 , Stefanie Haustein  3   9
Affiliations

The state of OA: a large-scale analysis of the prevalence and impact of Open Access articles

Heather Piwowar et al. PeerJ. .

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.

Keywords: Bibliometrics; Libraries; Open access; Open science; Publishing; Scholarly communication; Science policy; Scientometrics.

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Conflict of interest statement

Heather Piwowar and Jason Priem are founders of Impactstory, a non-profit company which makes Unpaywall, oaDOI, and other tools to improve scholarly communication.

Figures

Figure 1
Figure 1. Percent of articles by OA status, Crossref-DOIs sample vs Unpaywall-DOIs sample.
Figure 2
Figure 2. Number of articles (A) and proportion of articles (B) with OA copies, estimated based on a random sample of 100,000 articles with Crossref DOIs.
Figure 3
Figure 3. Number (A) and proportion (B) of articles with OA copies, by publisher, for the 20 most prolific publishers. Based on sample of 27,894 Crossref DOI-assigned articles published between 2009–2015.
Figure 4
Figure 4. Percentage of different access types of a random sample of WoS articles and reviews with a DOI published between 2009 and 2015 per NSF discipline (excluding Arts and Humanities).
Figure 5
Figure 5. Average relative citations of different access types of a random sample of WoS articles and reviews with a DOI published between 2009 and 2015.
Figure 6
Figure 6. Percentage and impact of different access types of a random sample of WoS articles and reviews with a DOI, by year of publication.
See this image and copyright information in PMC

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