Measuring open access publications: a novel normalized open access indicator


The issue of open access (OA) to scientific publications is attracting growing interest within the scientific community and among policy makers. Open access indicators are being calculated. In its 2019 ranking, the “Centre for Science and Technology Studies” (CWTS) provides the number and the share of OA publications per institution. This gives an idea of the degree of openness of institutions. However, not taking into account the disciplinary specificities and the specialization of institutions makes comparisons based on the shares of OA publications biased. We show that OA publishing practices vary considerably according to discipline. As a result, we propose two methods to normalize OA share; by WoS subject categories and by disciplines. Normalized Open Access Indicator (NOAI) corrects for disciplinary composition and allows a better comparability of institutions or countries.

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Fig. 1

Source Computed by author using OST-WoS database

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Source Computed by author using OST-WoS database

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Source Computed by author using OST-WoS database

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Source Computed by author using OST-WoS database

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Source Computed by author using OST-WoS database

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Source Computed by author using OST-WoS database

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Source Computed by author using OST-WoS database

Fig. 8

Source Computed by author using OST-WoS database


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The author would like to thank Frédérique Sachwald, Lesya Baudoin and Mathieu Goudard for their comments on an earlier version and for their guidance in improving the manuscript. The author also wishes to thank the referees for their comments and suggestions, which have contributed to improve the paper.

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Correspondence to Abdelghani Maddi.



See Tables

Table 3 OA share, NOAI and OA number of publications by country, 2015–2017


Table 4 OST disciplines

4 and

Table 5 ERC based classification.


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Maddi, A. Measuring open access publications: a novel normalized open access indicator. Scientometrics 124, 379–398 (2020).

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  • Open access
  • Normalization
  • Institutions
  • Disciplinary differences
  • Bibliometric indicators

MSC codes

  • 01-08
  • 00Axx

JEL codes

  • C43
  • L82
  • D83