Table 3. Studies included in the meta-synthesis: Main findings.

Study	% OA by discipline (year)	% OA route by discipline (year)
		Gold	Green	Hybrid	Bronze
Larivière and Sugimoto (2018)	All disciplines: 66% (2009–2017)    Biomedical Research: 85%    Clinical Medicine: 79%    Health: 73%    Mathematics: 67%    Earth and Space: 57%    Psychology: 56%    Physics: 56%    Biology: 51%    Professional Services: 42%    Social Sciences: 39%    Chemistry: 35%    Engineering and Technology: 29%	Not assessed	Not assessed	Not assessed	Not assessed
Piwowar et al. (2018)	All disciplines: 36.1% (2009–2015)    Biomedical Research: 58.5%    Mathematics: 52.7%    Clinical Medicine: 47.8%    Health: 41.8%    Earth and Space: 40.4%    Biology: 32.7%    Physics: 31.6%    Psychology: 29.7%    Social Sciences: 25.1%    Professional Fields: 20.6%    Engineering and Technology: 17.4%    Chemistry: 15.5%	All disciplines: 7.4% (2009–2015)    Biomedical Research: 15.3%    Health: 11.7%    Mathematics: 11.2%    Clinical Medicine: 10.3%    Biology: 7.3%    Earth and Space: 5.6%    Psychology: 4.7%    Engineering and Technology: 4.2%    Physics: 3.1%    Humanities: 3.0%    Chemistry: 2.8%    Arts: 2.4%    Professional Fields: 1.4%    Social Sciences: 1.3%	All disciplines: 11.5% (2009–2015)    Physics: 23.6%    Mathematics: 22.7%    Social Sciences: 18.7%    Psychology: 17.6%    Health: 14.1%    Professional Fields: 13%    Biomedical Research: 10%    Clinical Medicine: 9.8%    Earth and Space: 8.5%    Engineering and Technology: 8.3%    Chemistry: 7.9 %    Biology: 7.2%    Humanities: 6.3%    Arts: 4.9%	All disciplines: 0.6% (2009–2015)    Mathematics: 9.4%    Humanities: 8.6%    Biomedical Research: 8.1%    Clinical Medicine: 6.3%    Biology: 4.2%    Health: 3.0%    Earth and Space: 2.7%    Chemistry: 2.3%    Physics: 2.1%    Psychology: 2%    Professional Fields: 1.8%    Engineering and Technology: 1.8%    Social Sciences: 1.8%    Arts: 0.6%	All disciplines: 12.9% (2009–2015)    Biomedical Research: 25.2%    Earth and Space: 23.7%    Clinical Medicine: 21.5%    Biology: 14%    Health: 13%    Mathematics: 9.4%    Arts: 6.7%    Psychology: 5.4%    Professional Fields: 4.4%    Social Sciences: 3.3%    Humanities: 3.2%    Engineering and Technology: 3.2%    Physics: 2.9%    Chemistry: 2.5%
Bosman and Kramer (2018)	All disciplines: 29.4% (2016)    Life Sciences & Biomedicine: 41.7%    Social Sciences: 17.3%    Physical Sciences/Technology: 14.8%    Arts & Humanities: 13.9%	Not assessed	Not assessed	Not assessed	Not assessed
Science-Metrix (2018)	All disciplines: 55% (2014)    Health Sciences: 59%    Natural Sciences: 55%    Applied Sciences: 47%    Economic & Social Sciences: 44%    Arts & Humanities: 24%	All disciplines: 23% (2014)    Health Sciences: 33%    Natural Sciences: 15%    Applied Sciences: 13%    Economic and Social Sciences:    8%    Arts and Humanities: 7%	All disciplines: 31% (2014)    Health Sciences: 33%    Applied Sciences: 29%    Natural Sciences: 15%    Arts and Humanities: 9%    Economic and Social    Sciences: 8%	Not assessed	Not assessed
Martín-Martín et al. (2018)	All disciplines: 54.6% (2009, 2014)    Medical and Life Sciences: 60%    Natural Sciences: 50%    Social and Behavioral Sciences: 49.9%    Engineering Sciences: 40.2%    Language, Information and Communication: 36.3%    Law, Arts and Humanities: 32.3%	All disciplines: 7.3% (2009, 2014)    Medical and Life Sciences: 8.2%    Law, Arts and Humanities: 7.3%    Language, Information and Communication: 5.7%    Natural Sciences: 3.5%    Engineering Sciences: 3.5%    Social and Behavioral Sciences: 1.7%	All disciplines: 10.8% (2009, 2014)    Medical and Life Sciences: 19.4%    Social and Behavioral Sciences: 15.9%    Natural Sciences: 15.3%    Engineering Sciences: 8.7%    Law, Arts and Humanities: 5%    Language, Information and Communication: 4.4%	All disciplines: 1% (2009, 2014)    Law, Arts and Humanities: 1.8%    Medical and Life Sciences. 1.4%    Language, Information and Communication: 1.2%    Social and Behavioral Sciences: 0.5%    Natural Sciences: 0.5%    Engineering Sciences: 0.3%	All disciplines: 13.2% (2009, 2014)    Medical and Life Sciences. 20.8%    Natural Sciences: 7.5%    Engineering Sciences: 3%    Social and Behavioral Sciences: 5.3%    Law, Arts and Humanities: 0.1%    Language, Information and Communication: 0%
Jamali and Nabavi (2015)	All disciplines: 61.1% (2004– 2014)    Life Sciences: 66.9%    Social Sciences: 60.8%    Physical Sciences: 60%    Health Sciences: 59.7%	All disciplines: 49.4% (2004– 2014)    Life Sciences: 60.9%    Health Sciences: 56.4%    Physical Sciences: 40.4%    Social Sciences: 40.4%	All disciplines: 8.8% (2004–2014)    Physical Sciences: 18.3%    Social Sciences: 14.3%    Life Sciences: 2.5%    Health Sciences: 0.5%	Not assessed	Not assessed
Khabsa and Giles (2014)	All disciplines: 24% (all years)    Computer Science: 50%    Multidisciplinary Sciences: 43%    Economics and Business: 42%    Geosciences: 35%    Physics: 35%    Environmental Sciences: 29%    Mathematics: 27%    Medicine: 26%    Biology: 25%    Arts and Humanities: 24%    Chemistry: 22%    Social Sciences: 19%    Agricultural Science: 12%    Engineering: 12%    Material Science: 12%	Not assessed	Not assessed	Not assessed	Not assessed
European Commission (2014)	All disciplines: 53.7% (2011 – 2013)    General Science & Technology: 89.7%    Biomedical Research: 70.6%    Mathematics & Statistics: 67.6%    Biology: 66.2%    Physics & Astronomy: 59.4%    Earth & Environmental: 57.8%    Psychology & Cognitive Sciences: 57.7%    Public Health & Health Services: 57.2%    Clinical Medicine: 56.3%    Sciences Economics & Business: 54.9%    Information & Communication Technology: 54.0%    Agriculture, Fisheries & Forestry: 53.8%    Social Sciences: 43.7%    Enabling & Strategic Technologies: 39.3%    Chemistry: 38.5%    Built Environment & Design: 37.5%    Arts, Humanities & Social Sciences: 35.9%    Philosophy & Theology: 34.7%    Engineering: 34.6%    Historical Studies: 34.4%    Communication & Textual Studies: 30.9%    Visual & Performing Arts: 23.3%	All fields: 12.1% (2011–2013)    Gen. Science & Technology: 58.0%    Biology: 17.0%    Agriculture, Fisheries & Forestry: 16.1%    Public Health & Health Services: 15.8%    Clinical Medicine: 14.8%    Biomedical Research: 12.4%    Information & Communication Technologies: 12.4%    Mathematics & Statistics: 11.4%    Chemistry: 9.5%    Enabling & Strategic Technologies: 9.3%    Social Sciences: 8.7%    Communication & Textual Studies: 8.7%    Earth & Environmental Sciences: 8.1%    Historical Studies: 7.2%    Psychology & Cognitive Sciences: 5.6%    Economics & Business: 5.4%    Philosophy & Theology: 5.1%    Physics & Astronomy: 5.1%    Engineering: 4.1%    Built Environment & Design: 3.5%    Visual & Performing Arts: 2.8%    Gen. Arts, Humanities Social Sciences: 2.6%	All fields: 5.9% (2011–2013)    Physics & Astronomy: 25.6%    Mathematics & Statistics: 24.3%    Economics & Business: 11.3%    Information & Communication Technologies: 8.7%    Earth & Environmental Sciences: 5.6%    Social Sciences: 5.2%    Philosophy & Theology: 5.1%    Built Environment & Design: 4.6%    Gen. Science & Technology: 3.9%    Biology: 3.7%    Psychology & Cognitive Sciences: 3.6%    Communication & Textual Studies: 3.6%    Gen. Arts, Humanities & Social Sciences: 3.5%    Engineering: 3.2%    Public Health & Health Services: 3%    Visual & Performing Arts: 2.9%    Agriculture, Fisheries & Forestry: 2.8%    Enabling & Strategic Technologies: 2.7%    Historical Studies: 2.5%    Clinical Medicine: 2.2%    Biomedical Research: 2.1%    Chemistry: 1.8%	Not assessed	Not assessed
Gargouri et al. (2012)	All disciplines: 23% (2010)    Mathematics: 42%    Earth & Space: 37%    Social Sciences: 37%    Professional Fields: 29%    Physics: 27%    Engineering & Technology: 23%    Psychology: 23%    Biology: 22%    Humanities: 19%    Health: 17%    Clinical Medicine: 14%    Arts: 14%    Biomedical Research: 12%    Chemistry: 9%	All disciplines: 2% (2005–2010)    Biomedical Research: 8%    Clinical Medicine: 5%    Health: 5%    Mathematics: 2%    Physics: 2%    Earth & Space: 2%    Biology: 2%    Engineering & Technology: 1%    Psychology: 1%    Social Sciences: 1%    Chemistry: 1%    Arts: 1%    Humanities: 1%    Professional Fields: 1%	All disciplines: 21% (2005– 2010)    Mathematics: 43%    Earth & Space: 36%    Professional Fields: 29%    Physics: 26%    Engineering & Technology: 23%    Social Sciences: 35%    Psychology: 27%    Biology: 22%    Humanities: 14%    Health: 12%    Chemistry: 10%    Clinical Medicine: 9%    Arts: 9%    Biomedical Research: 6%	Not assessed	Not assessed
Björk et al. (2012)	All disciplines: 20.4% (2008)    Earth Sciences: 32.9%    Mathematics: 25.6%    Physics & Astronomy: 23.5%    Social Sciences: 23.5%    Medicine: 21.7%    Biochemistry, Genetics & Molecular Biology: 19.9%    Engineering: 18.4%    Other areas related to Medicine: 15.2%    Chemistry and Chemical Engineering: 12.9%	All disciplines: 8.5% (2008)    Medicine: 13.9%    Biochemistry, Genetics & Molecular Biology: 13.7%    Other areas related to Medicine: 10.6%    Mathematics: 8.1%    Earth Sciences: 7%    Social Sciences: 5.6%    Chemistry and Chemical Engineering: 5.5%    Engineering: 4.8%    Physics & Astronomy: 3%	All disciplines: 11.9% (2008)    Earth Sciences: 25.9%    Physics & Astronomy: 20.5%    Social Sciences: 17.9%    Mathematics: 17.5%    Engineering: 13.6%    Medicine: 7.8%    Chemistry and Chemical Engineering: 7.4%    Biochemistry, Genetics & Molecular Biology: 6.2%    Other areas related to Medicine: 4.6%	Not assessed	Not assessed
Hajjem et al. (2006)	All disciplines: Not reported (1992 – 2003)    Sociology: 16%    Biology: 15%    Economics: 13.5%    Business: 9%    Management: 7%    Psychology: 7%    Health: 6.2%    Political Science: 5.3%    Education: 5.3%    Law: 5.1%	Not assessed	Not assessed	Not assessed	Not assessed