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This document forms a part of a series of reports produced as part of the European Commission Contract RTD-B6-PP-2011-2—Study to develop a set of indicators to measure open access:


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This study report assesses the free availability of scholarly publications during the 1996 to 2013 period. It is the largest scale measurement of open access availability performed to date: a sample of one-quarter of a million records was used to study the historical evolution of open access (OA) between 1996 and 2013 and a larger, one million records sample was used to perform an in-depth assessment of the proportion and scientific impact of OA between 2008 and 2013 in different types of OA, for different scientific fields of knowledge, and for 44 countries, the EU28, ERA, and the world.

Compared to previous studies done on the availability of OA, the present study presents the following characteristics: (1) it used the Scopus database, which currently covers a broader range of journals from various countries and scientific disciplines than other comprehensive databases; (2) it uses a simple definition of OA—freely available online to all (no money had to be paid, no registration to a service or website had to be made); (3) it used huge samples to maximise statistical precision; (4) it made careful and extensive efforts to harvest papers wherever they could be downloaded for free, without restriction, rather than restricting the approach to a search engine (in order to obtain a high 'recall' rate, that is, the capacity to retrieve a large part of the relevant records, while, in addition, carefully minimising the number of false records collected (that is, the approach maximised retrieval precision); and (5) it carefully characterised the strengths and weaknesses of the measurement instrument in order to apply a correction that would provide a truer measure based on an Adjusted OA score.

This study also provided a series of rational definitions of access, open access, and ideal open access. The definitions provided examine aspects such as restrictions, payment, delay, transiency, and legitimacy. Because of the limited means (time and budget) available for this project, it was necessary to use operational definitions of OA which do not provide all the details one may wish to obtain. Though it was easy to obtain a clear and easily operational definition of Gold OA by stating that it referred to papers published in Gold OA journals listed in the Directory of Open Access Journals, defining and measuring Green OA was more challenging. The operational definition restricted Green OA to researchers' self-archived papers in institutional and some thematic repositories listed in OpenDOAR and ROAR. This left a sizeable residual number of papers that could still be downloaded for free; these were classified as Other OA. This comprises, for example, Gold OA papers from subscription-based journals, which are made available through article processing charges (APC). Other OA also include papers available in large repositories such as PubMed Central and aggregator sites such as CiteSeerX. There are also Robin Hood OA or Rogue OA papers, that is, papers that infringe on copyrights by making them accessible to the public despite licenses that restrict them to being behind pay walls.