Support for the open access (OA) movement is increasing, yet the majority of OA articles do not have a license that permits free re-use of contents, and so do not fully comply with the 2002 Budapest OA Initiative (BOAI) definition of OA. In a recent study by Piwowar et al, representative samples were taken from the online databases Crossref, Web of Science and Unpaywall (100,000 articles from each) to determine the prevalence and type of OA publications. Importantly, this involved categorisation of articles as follows:
- gold OA – published in an OA journal indexed by the Directory of OA Journals (DOAJ)
- green OA – paid-for access via the publisher’s webpage but free access in an OA repository
- hybrid OA – OA in a journal that also publishes non-OA articles
- ‘bronze’ OA – free to read on the publisher’s webpage but without a license permitting free re-use of content
- closed access – all other articles.
The most common form of OA was ‘bronze’. This may have implications for research; the lack of a license permitting the free re-use of an article’s contents can substantially restrict the impact of the data therein, for example by preventing other groups from conducting further analyses. In a recent Nature Index article, Piwowar notes that in the current age of machine learning and ‘big data’, it is especially important that data are freely available for computational analysis. Overall, the study found that 47% of articles were OA in 2015 (the most recent year of analysis), and the authors predict that all articles could be OA by 2040. Despite this encouraging forecast, the future of OA may be less bright if bronze OA continues to prevail.