
The Open Access Citation Advantage: List of studies and results to date

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Study Atchison A & Bull J (2015) Will OA get me cited? An analysis of the efficacy of Open Access publishing in Political Science. PS: Political Science & Politics, (forthcoming).
Disciplinary area Political science
Sample Unclear (preview abstract only available at time of access, 15th Nov 2014). Articles from 8 political science journals.
Basic analytical approach Compared mean citation rates between OA and subscription-only articles from the same journals.
Filtered out self-citations? No
Citation advantage? Yes; “OA publication results in a clear citation advantage”.
Attribution of advantage to a particular OA component? Not examined
Study Donovan JM, Watson CA & Osborne C (2014) The Open Access Advantage for American Law Reviews. Available at SSRN: http://ssrn.com/abstract=2506913 or http://dx.doi.org/10.2139/ssrn.2506913
Disciplinary area Law
Sample 3,489 OA articles and 2,553 non-OA articles (total 6,042) in 30 journals
Basic analytical approach Compared citations accrued per year for OA articles to those for articles published in the same journals but not made OA. Time elapsed for citations to accrue: up to 23 years.
Filtered out self-citations? No
Citation advantage? Yes. Across all data, OA articles accrued 49% more citations per year than non-OA articles. Citation advantage was lower for OA articles in higher tier journals, in which articles are expected to be highly cited even if non-OA.
Attribution of advantage to a particular OA component? Not examined
Study Frisch NK, Nathan R, Ahmed YK & Shidham VB (2014) Authors attain comparable or slightly higher rates of citation publishing in an Open Access journal (CytoJournal) compared to traditional cytopathology journals – a five year (2007-2011) experience. CytoJournal, 11:10. doi: 10.4103/1742-6413.131739.
Disciplinary area Cytopathology
Sample 314 publications by 28 authors.
Basic analytical approach Compared citations to articles by the same authors published in OA and non-OA journals. Time elapsed for citations to accrue: 5 years.
Filtered out self-citations? No
Citation advantage? Publications in OA journals received significantly more citations on average than those in non-OA journals (p<0.05). However, with meeting abstracts excluded from the data set, the difference was non-significant (p=0.57).
Attribution of advantage to a particular OA component? Not examined
Study Koler-Povh T, Juznic P & Turk G (2014) Impact of Open Access on citation of scholarly publications in the field of civil engineering. Scientometrics, 98(2): 1033–1045.
Disciplinary area Civil engineering
Sample 2,026 articles (442 OA) published in 2007 in 14 journals
Basic analytical approach Compared average citations per article between OA and non-OA articles published in the same journals. Time elapsed for citations to accrue: 5 years.
Filtered out self-citations? No
Citation advantage? Yes; overall, the average number of citations per article was significantly higher for OA than non-OA articles. OA articles formed 22% of the sample but received 29% of total citations to the sample. This pattern held true for all higher-impact journals studied and for some medium-impact journals, but not for lower-impact journals.
Attribution of advantage to a particular OA component? Not examined
Study Kullman L (2014) The Effect of Open Access on Citation Rates of Self-archived Articles at Chalmers. In IATUL 2014–35th Annual Conference–Aalto University, Espoo, Finland, 2-5 June 2014.
Disciplinary area All
Sample 3470 articles (899 OA) archived in the Chalmers University of Technology (Göteborg, Sweden) university repository.
Basic analytical approach Compared mean normalized citation scores (MNCS; number of citations normalized by field and publication year) between articles listed with full-text or bibliographical data only on the university repository.
Filtered out self-citations? No
Citation advantage? Yes; full-text articles had a 22% higher citation rate than those with bibliographical data only, and this difference was significant.
Attribution of advantage to a particular OA component? Not examined
Study McCabe MJ and Snyder CM (2014) Identifying the effect of Open Access on citations using a panel of science journals. Economic Inquiry, 52(4): 1284–1300.
Disciplinary area Ecology, botany, multidisciplinary science and biology
Sample Over 200,000 articles published in 100 journals from 1996 to 2005.
Basic analytical approach Compared number of citations to full volumes of fully OA journals to volumes of journals made partially OA and non-OA journal volumes. Time elapsed for citations to accrue: up to 10 years.
Filtered out self-citations? No
Citation advantage? Yes, overall: an citation increase of 8% is found for the full data set. However, depends on journal impact. Citations to high-ranked journals increased significantly with OA, but citations to low-ranked journals decreased significantly with OA.
Attribution of advantage to a particular OA component? Suggests OA facilitates more efficient cross-referencing of work, increasing competition for readers’ attention and so benefitting higher-quality articles in higher-ranked journals.
Study Mueller-Langer F & Watt R (2014) The Hybrid Open Access Citation Advantage: How Many More Cites is a $3,000 Fee Buying You? Max Planck Institute for Innovation & Competition Research Paper No. 14-02. Available at SSRN: http://ssrn.com/abstract=2391692 or http://dx.doi.org/10.2139/ssrn.2391692
Disciplinary area Economics
Sample 1,329 articles (208 OA) published in 15 hybrid journals between 2000 and 2011.
Basic analytical approach Compared number of citations between articles published OA and non-OA in the same journals. Time elapsed for citations to accrue: 1-12 years.
Filtered out self-citations? Yes
Citation advantage? No; although there were significantly more citations to OA than non-OA articles, the significance was removed by controlling for institution quality and existence of an OA pre-print.
Attribution of advantage to a particular OA component? Not examined
Study Sabharwal S, Patel N & Johal K (2014) Open Access publishing: a study of current practices in orthopaedic research. International Orthopaedics, 38(6): 1297–1302.
Disciplinary area Orthopaedics
Sample All 63 orthopaedic journals listed in Journal Citation Report 2012 (20 hybrid and 5 full OA)
Basic analytical approach Compared impact factor and citation numbers between subscription-only, hybrid, and full OA journals.
Filtered out self-citations? No
Citation advantage? No; no difference between OA and subscription journals on the basis of impact factor or citation number.
Attribution of advantage to a particular OA component? Not examined
Study Wohlrade K & Birkmeier D (2014) Do Open Access articles in economics have a citation advantage? Available at: http://mpra.ub.uni-muenchen.de/56842/
Disciplinary area Economics
Sample 639 articles published in 13 economics journals in 2005.
Basic analytical approach Compared mean number of citations between articles published OA and non-OA. Time elapsed for citations to accrue: 7 years.
Filtered out self-citations? No
Citation advantage? Yes; OA articles have on average a 307.9% higher citation count than non-OA articles.
Attribution of advantage to a particular OA component? Not examined
Study Aman V (2013) The potential of preprints to accelerate scholarly communication – a bibliometric analysis based on selected journals. MA Thesis. Humboldt University of Berlin, Germany.
Disciplinary area High Energy Physics, mathematics, astrophysics, quantitative biology, library and information science
Sample Articles from 13 journals from fields publishing to arXiv
Basic analytical approach Compared speed until first citation and total number of citations between articles published with an OA arXiv preprint and those without. Many journals examined offered OA options but the OA status of each article was not recorded. Time elapsed for citations to accrue: not specified.
Filtered out self-citations? No
Citation advantage? In all fields examined except biology, articles received more citations and more quickly if an OA preprint was published on arXiv.
Attribution of advantage to a particular OA component? Not examined
Study Koler-Povh T, Turk G and Juni P (2013) Does the Open Access business model have a significant impact on the citation of publications? Case study in the field of civil engineering. Proceedings of the Fifth Belgrade International Open Access Conference 2012. DOI: 10.5937/BIOAC-68.
Disciplinary area Civil engineering.
Sample 286 articles from three international civil engineering journals.
Basic analytical approach Compared citations (per Google Scholar and ISI WOS) to OA and non-OA articles in the same journals for articles published in 3 journals during 2007. Time elapsed for citations to accrue: 5 years.
Filtered out self-citations? No
Citation advantage? Yes, overall, but significance varied according to both rank of journal (only the highest-ranked journal had a significant citation advantage in both citation databases) and data source (one journal had a significant citation advantage according to GS data but not WOS).
Attribution of advantage to a particular OA component? Not examined
Study Laakso M and Björk BC (2013) Delayed open access: An overlooked high-impact category of openly available scientific literature. Journal of the American Society for Information Science and Technology, 64(7): 1323–1329.
Disciplinary area All
Sample 492 journals publishing 111,312 articles in 2011. 77.8% of articles were made OA (green route) within 12 months of publications and 85.4% within 24 months
Basic analytical approach Compared 2010 impact factors between “delayed OA journals” (those permitting green OA), gold OA journals and subscription-only journals. Time elapsed for citations to accrue: impact factors are based on 5 years of citations.
Filtered out self-citations? No
Citation advantage? Yes; on average, green OA journals have twice as high citation rates than subscription-only journals, and three times as high as immediate OA journals.
Attribution of advantage to a particular OA component? Not examined
Study McCabe MJ & Snyder CM (2013) Does online availability increase citations? Theory and evidence from a panel of economics and business journals. Available at SSRN: http://mccabe.people.si.umich.edu/McCabe_Snyder_ReStat_2013.pdf
Disciplinary area Economics and business
Sample 100 journals, including all journals in economics and business available on JSTOR
Basic analytical approach Compared number of citations per year to journals made available online and print-only journals, regardless of OA status. Journal volume included in models as a fixed effect, to try and control for article quality.
Filtered out self-citations? No
Citation advantage? No; inclusion of journal volume as a fixed effect masked citation advantage.
Attribution of advantage to a particular OA component? Suggests that article quality is difficult to quantify and has therefore been overlooked in previous studies.
Study Piwowar HA and Vision TJ (2013) Data reuse and the open data citation advantage. PeerJ, 1: e175. http://dx.doi.org/10.7717/peerj.175
Disciplinary area Genetics
Sample 10,557 papers that had generated gene expression microarray data and had citation counts in Scopus.
Basic analytical approach Compared number of citations to papers that had made their datasets openly available through either of the two most widely-used gene expression microarray repositories with those that had not published their data. OA status of the original paper was controlled as a covariate. Time elapsed for citations to accrue: 2-10 years.
Filtered out self-citations? No
Citation advantage? Yes. Papers with openly available datasets received on average 9% (95% confidence interval: 5% to 13%) more citations than those with unpublished data.
Attribution of advantage to a particular OA component? Suggests data reuse directly increases citations. Manual review of 138 citations revealed 6% (95% CI: 3% to 11%) were attributions for data reuse.
Study Riera M and Aibar E (2013) ¿Favorece la publicación en abierto el impacto de los artículos cientificos? Un studio empírico en el ámbito de la medicina intensiva [Does open access publishing increase the impact of scientific articles? An empirical study in the field of intensive care medicine]. Medícina Intensiva, 37(4): 232–240.
Disciplinary area Intensive care medicine
Sample 161 articles published in Medícina Intensiva in 2008, of which 76% were non-OA
Basic analytical approach Compared raw number of citations between OA and non-OA articles. Time elapsed for citations to accrue: 2-3 years.
Filtered out self-citations? No
Citation advantage? Yes; open access articles received more monthly citations on average than non-open access articles. Although there was no significant difference in raw number of citations between all open access and non-open access articles, there was a significant difference in number of citations between the most highly cited open access and non-open access articles.
Attribution of advantage to a particular OA component? Not examined
Study Rivers C (2013) Scholarly impact of Open Access journals, Epicurve Blog. Viewed 1st November 2014, http://www.caitlinrivers.com/blog/open-access-journal-impact-statistics
Disciplinary area All
Sample Journals listed in the Directory of Open Access Journals
Basic analytical approach Compared two measures of journal impact, Source-Normalized Impact per Paper (SNIP) and SCImago Journal Rank (SJR) between OA and non-OA journals.
Filtered out self-citations? No
Citation advantage? No; both measures of journal impact were lower for OA than non-OA journals.
Attribution of advantage to a particular OA component? Not examined
Study Solomon DJ, Laakso M and Björk BC (2013) A longitudinal comparison of citation rates and growth among open access journals. Journal of Informetrics (accepted).
Disciplinary area All
Sample 2,012 OA journals and 16,121 subscription journals.
Basic analytical approach Compared SNIP2 (Source-Normalized Impact per Paper –a field-adjusted citation impact measure) for OA journals funded by article processing charges (APCs), OA journals funded by other means, and subscription journals
Filtered out self-citations? No
Citation advantage? No; SNIP2 averages for APC-funded OA journals were roughly equal to or lower than those for subscription journals, whilst those for other OA journals were lower still.
Attribution of advantage to a particular OA component? Not examined
Study Vanclay JK (2013) Factors affecting citation rates in environmental science. Journal of Informetrics, 7, 265–271.
Disciplinary area Environmental science
Sample 131 publications by members of the School of Environmental Science and Management at Southern Cross University during 2006–2007
Basic analytical approach Coded OA status of publications as a ternary variable: 0 = subscription journal, 1 = green OA, 2 = gold OA. Tested for Pearson correlations between OA status and citations per year. Time elapsed for citations to accrue: 5-6 years.
Filtered out self-citations? No
Citation advantage? No; there was no significant correlation between OA status and citation rates.
Attribution of advantage to a particular OA component? Not examined
Study Björk BC and Solomon D (2012) Open access versus subscription journals: a comparison of scientific impact. BMC Medicine, 10: 73.
Disciplinary area All
Sample 610 OA journals compared with 7,609 subscription journals using Web of Science data, and an overlapping set of 1,327 OA journals compared with 11,124 subscription journals using Scopus data
Basic analytical approach Compared 2-year impact factors of OA and subscription journals, controlling for journal age, country of publisher, discipline and OA business model.
Filtered out self-citations? No
Citation advantage? No; average citation rates were about 30% higher for subscription journals than for OA journals. After controlling for discipline, age of journal, and location of publisher, the difference was removed for most subcategories.
Attribution of advantage to a particular OA component? Not examined
Study Kim, H (2012) The effect of free access on the diffusion of scholarly ideas. MIS Speaker’s Series, University of Arizona, 24th January 2012.
Disciplinary area Social science
Sample 385 articles made freely available on the Social Science Research Network (SSRN) at least 4 years after publication, and 3,820 articles published in the same journal issues but not freely available online
Basic analytical approach Compared number of citations to papers made retrospectively OA by posting to SSRN before and after they became freely available with citations to papers in the same journals not made freely available.
Filtered out self-citations? Yes
Citation advantage? Yes; although articles posted to SSRN were on average more highly-cited than the non-OA articles even before being made OA, the difference in citations per year between SSRN OA articles and non-OA controls became greater after posting to SSRN.
Attribution of advantage to a particular OA component? Not examined
Study Mahesh G (2012) Open access and impact factors. Current Science, 103(6), 610.
Disciplinary area Science communication and information resources
Sample 17 primary journals published by the National Institute of Science Communication and Information Resources, India
Basic analytical approach Analysed change in impact factors of NISCAIR journals over the years surrounding 2008-09, when all NISCAIR journals became OA.
Filtered out self-citations? No
Citation advantage? Yes; almost all of the 17 journals increased their impact factors in the years immediately following the switch to OA.
Attribution of advantage to a particular OA component? Not examined
Study Xia J and Nakanishi K (2012) Self-selection and the citation advantage of open access articles. Online Information Review, 36(1): 40–51.
Disciplinary area Anthropology
Sample Unclear: article is not open access and abstract only was viewed
Basic analytical approach Compared citations between OA and non-OA articles separately for high-ranked and low-ranked journals.
Filtered out self-citations? No
Citation advantage? Yes, overall. Articles in lower-ranked journals also had a greater rate of citations if made OA. However, articles in high-ranked journals did not have a higher citation rate if made OA.
Attribution of advantage to a particular OA component? Not examined
Study Davis PM (2011) Do discounted journal access programs help researchers in sub-Saharan Africa? A bibliometric analysis. Learned Publishing, 24: 287–298.
Disciplinary area Agriculture and allied subjects
Sample 19,753 articles published between 1988 and 2009 at 70 institutions in 11 African countries
Basic analytical approach Compared number of citations to journals included in The Essential Electronic Agricultural Library (TEEAL) from subscribing and non-subscribing institutions in Africa. TEEAL is a large collection of research articles from leading scientific journals sold for a nominal fee to research institutions in the world’s poorest countries, thereby effectively providing free access for researchers at those institutions.
Filtered out self-citations? No
Citation advantage? Yes; articles published from TEEAL-subscribing institutions contained an average of 0.4 more citations to articles included in TEEAL.
Attribution of advantage to a particular OA component? Suggests that access to subscription-only literature is a limiting resource to scientists in low-income countries, and therefore that such scientists are more likely to cite freely-available articles.
Study Davis PM (2011) Open access, readership, citations: a randomized controlled trial of scientific journal publishing. The FASEB Journal, doi:10.1096/fj.11–183988.
Disciplinary area Sciences, social sciences and humanities
Sample 3245 articles (of which 712 are OA) published in 36 journals
Basic analytical approach Compared article downloads 12 months after publication and citations after 3 years between gold OA and non-OA/green OA articles
Filtered out self-citations? No
Citation advantage? No; OA articles were not cited more frequently than subscription-access articles. However, full-text HTML and PDF versions of OA articles were downloaded significantly more frequently during the first 12 months.
Attribution of advantage to a particular OA component? Suggests that most scientific authors are concentrated at research universities with excellent access to subscription-access literature.
Study Donovan JM & Watson CA (2011) Citation advantage of Open Access legal scholarship. Law Library Journal, 103(4): 553–573.
Disciplinary area Law
Sample 566 articles (of which 124 were OA) published in three law journals between 1990 and 2008.
Basic analytical approach Compared annual citations to OA and non-OA articles within the same journals. Time elapsed for citations to accrue: up to 18 years.
Filtered out self-citations? No
Citation advantage? Yes; OA articles received on average 58% more citations than non-OA articles of similar age and quality in the same journal.
Attribution of advantage to a particular OA component? Not examined
Study Ingwersen P & Elleby A (2011) Do Open Access working papers attract more citations compare to printed journal articles from the same research unit? In: Proceedings 13th International Conference of the International Society for Scientometrics & Informetrics, Durban, South Africa, 4th-7th July 2011.
Disciplinary area Multidisciplinary social science
Sample 10 OA non-peer reviewed working papers and 10 printed peer reviewed journal articles
Basic analytical approach Compared number of citations (from Web of Science and Google Scholar data) to OA working papers and non-OA journal articles published in the same year (2004) by the same institute (Danish Institute for International Studies, Copenhagen) and predominately the same authors. Time elapsed for citations to accrue: 5 years.
Filtered out self-citations? Yes
Citation advantage? No; OA working papers were far less cited than peer-reviewed journal articles.
Attribution of advantage to a particular OA component? Not examined
Study Wang ML (2011) The impact of open access journals on library and information scientists’ research in Taiwan. In Asia-Pacific Conference On Library & Information Education & Practice 2011 (A-LIEP2011), 22-24th June 2011, Malaysia.
Disciplinary area Library and information science
Sample 745 articles published by 72 LIS scholars in Taiwan between 2000 and 2009, of which 66.98% were OA
Basic analytical approach Mean citation rate to OA and non-OA articles published by Taiwanese LIS researchers was compared. Time elapsed for citations to accrue: 2-11 years.
Filtered out self-citations? No
Citation advantage? Yes; OA articles received citations on average 1.29 times as fast.
Attribution of advantage to a particular OA component? Not examined
Study Xu L, Liu J & Fang Q (2011) Analysis on Open Access citation advantage: an empirical study based on Oxford Open journals. iConference ’11, Proceedings of the 2011 iConference, Seattle, 11th February 2011.
Disciplinary area Medicine, life sciences, mathematics & physical sciences, law, humanities, and social sciences
Sample 12,354 original research articles published in Oxford University Press journals in 2009, of which 1,487 were gold OA and 5,417 were green OA
Basic analytical approach Compared number of citations between gold OA, green OA and non-OA articles. Time elapsed for citations to accrue: 6-18 months.
Filtered out self-citations? No
Citation advantage? Yes; gold OA articles received 139% more citations than non-OA, and green OA received 23% more citations than non-OA. These results varied depending on subject area, and in the humanities, non-OA articles received more citations than OA.
Attribution of advantage to a particular OA component? Not examined
Study Calver MC & Bradley JS (2010) Patterns of citations of Open Access and non-Open Access conservation biology journal papers and book chapters. Conservation Biology, 24(3): 872–880.
Disciplinary area Conservation biology
Sample 584 articles (167 green OA) published in 6 journals during 2000, 326 articles (209 gold OA) published in 2 journals between 2005 and 2006, and 241 book chapters (15 green OA) published in 4 books between 2001 and 2005.
Basic analytical approach Compared number of citations between OA and non-OA articles and chapters from the same journal or book. Separate analyses for green OA, gold OA and green OA book chapters. Time elapsed for citations to accrue: 8 years (green OA); 2-3 years (gold OA); 3-7 years (green OA book chapters).
Filtered out self-citations? No
Citation advantage? Varied; although for all journals, mean number citations to both green and gold OA papers exceeded those to non-OA papers, these effects were non-significant (green OA: p=0.08; gold OA: p=0.14). However, the mean number of citations to green OA book chapters was at least twice that for non-OA chapters (p=0.02).
Attribution of advantage to a particular OA component? Suggests that self-archiving of book chapters may be of particular advantage to authors because these are frequently not abstracted online.
Study Davis PM (2010) Access, Readership, Citations: A randomized controlled trial of scientific journal publishing. Ph.D. Thesis. Cornell University: USA.
Disciplinary area Biological sciences, medical sciences, multi-disciplinary sciences, social sciences and humanities.
Sample 712 articles randomly assigned OA status and 2,553 subscription-access articles published in 36 journals between Jan 2007 and Feb 2008.
Basic analytical approach Randomly assigned Open Access status to a subset of articles that would otherwise have been published subscription-only. Compared article downloads, unique visitors and number of citations between these OA articles and subscription-only controls in the same set of journals. Time elapsed for citations to accrue: 2 years.
Filtered out self-citations? No
Citation advantage? No; OA articles received more article downloads and unique visitors but were cited no more frequently than subscription-access articles.
Attribution of advantage to a particular OA component? Suggests that the majority of scientific authors have excellent access to the scientific literature through their institutions; OA will mainly benefit communities that consume, but do not contribute to, the literature.
Study Davis PM (2010) Does Open Access lead to increased readership and citations? The Physiologist, 53(6): 197–201.
Disciplinary area Physiology
Sample 1,619 articles (of which 247 were OA) published in 11 American Physiological Society journals between January and April 2007
Basic analytical approach Compared downloads and citations between articles made OA immediately on publication and those made OA 12 months after publication in subscription-only journals. Time elapsed for citations to accrue: 3 years.
Filtered out self-citations? No
Citation advantage? No; gold OA articles were not more likely to be cited during the first year after publication and were cited no more frequently during the first three years than green OA articles. However, gold OA articles received significantly more full-text and PDF downloads than green OA articles during the first year than green OA articles (which were subscription-only during this period).
Attribution of advantage to a particular OA component? Suggests that scientific authors are adequately served by the current model of institutional subscription, but that there is a readership outside of the core research community who are not served by this model.
Study Gargouri Y, Hajjem C, Lariviere V, Gingras Y, Brody T, Carr L & Harnad S (2010) Self-Selected or Mandated, Open Access Increases Citation Impact for Higher Quality Research. PLoS ONE (Submitted). The study is ongoing and details can be found here: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0013636
Disciplinary area Engineering, Biology, biomedicine, chemistry, psychology, mathematics, clinical medicine, health, physics, social sciences, earth sciences
Sample 27,197 articles in 1984 journals. See Gargouri & Harnad, 2009. This is the updated version of that preprint
Basic analytical approach See Gargouri & Harnad, 2009. This is the updated version of that preprint. Time elapsed for citations to accrue: 2 to 6 years
Filtered out self-citations? Yes
Citation advantage? Yes, and size of OA advantage varies with discipline. There was no significant reduction in the OA advantage found with mandated or non-mandated status. The advantage found was independent of Journal Impact Factor, time since publication, number of references in the article and number of co-authors. Found that the increase in citations for OA articles is stronger for highly-cited articles. Articles from mandated institutions have increased citations in the medium-to-highly cited range. Review articles have increased citations and the effect is greatest in the highly-cited range.
Attribution of advantage to a particular OA component? Confirms other findings that suggest that the best quality (i.e. the most highly-cited) articles have most to gain, relatively, from OA. Also found no evidence to support the Selection Bias, since there was no difference in the citation advantage for mandated articles and non-mandated articles (i.e. those that might be preferentially made OA out of choice because their authors thought they were better examples of their work)
Study Snijder R (2010) The profits of free books – an experiment to measure the impact of Open Access publishing. Learned Publishing, 23(4): 293–301.
Disciplinary area Humanities and social sciences
Sample 400 books published by Amsterdam University Press before April 2009
Basic analytical approach Created 4 treatments with 100 books each: non-OA, freely available through Google Book Search, freely available through the AUP repository, and freely available through both channels. Compared monthly sales, citations and views for a 9-month period.
Filtered out self-citations? No
Citation advantage? No; no relation was found between OA status and citation rates. However, contrary to expectations, there was also no diminishing effect of OA status on sales.
Attribution of advantage to a particular OA component? Not examined
Study Xia J, Myers RL & Wilhoite SK (2010) Multiple Open Access availability and citation impact. Journal of Information Science, doi: 10.1177/0165551510389358.
Disciplinary area Library and information science
Sample 875 articles published in 2006 from 20 high-impact journals in LIS, of which 486 were OA
Basic analytical approach Compared number of citations between non-OA articles, those with a single searchable OA copy, and those with multiple OA copies available online. Time elapsed for citations to accrue: 4 years.
Filtered out self-citations? No
Citation advantage? Yes; OA articles received on average 2.13 more citations than non-OA articles. In addition, OA articles received on average 2.348 more citations per copy available online.
Attribution of advantage to a particular OA component? Not examined
Study Zawacki-Richter O, Anderson T & Tuncay N (2010) The growing impact of Open Access distance education journals: a bibliometric analysis. International Journal of E-learning and Distance Education, 24(3).
Disciplinary area Distance education
Sample 1,123 articles (573 OA) published in 12 distance education journals (6 OA, 6 subscription-only) between 2003 and 2008.
Basic analytical approach Compared average number of cites per paper for 6 OA and 6 subscription-only journals in the same field. Time elapsed for citations to accrue: 1-6 years.
Filtered out self-citations? No
Citation advantage? No; there was no significant difference between OA and subscription-only journals. There was some indication that OA articles may be cited more quickly after publication.
Attribution of advantage to a particular OA component? Not examined
Study Bernius S & Hanauske M (2009) Open Access to Scientific Literature – Increasing Citations as an Incentive for Authors to Make Their Publications Freely Accessible. 42nd Hawaii International Conference on System Sciences (HICSS ’09), 5-8 Jan. 2009, 1-9. http://www.is-frankfurt.de/publikationenNeu/OpenAccesstoScientificLiteratu3032.pdf
Disciplinary area Not an observational study
Sample Not an observational study
Basic analytical approach The authors developed a computer simulation of citation networks, using a range of assumptions for parameters, to model citing behaviour and outcomes. The methodology attempted to account for causation as well as model effect.
Filtered out self-citations? Not applicable
Citation advantage? Yes
Attribution of advantage to a particular OA component? Did not model Early Advantage: all modelling was on access from the moment of publication. Did not model Selection Bias specifically, either. The methodology randomly modelled high-impact and low-impact authors switching their strategy to making their articles Open Access: no Selection Bias signal was detected
Study Evans JA & Reimer J (2009) Open Access and Global Participation in Science. Science, 323(5917): 1025. http://www.auf.org/media/IMG2/pdf/Open_Access_and_Global_Participation_in_Science.pdf
Disciplinary area All
Sample 26 million articles in 8000 journals
Basic analytical approach Compared citations to OA or non-OA journals (not articles)
Filtered out self-citations? No
Citation advantage? Yes. The increase in citations with OA is 8% for newly-published articles, and twice as large for citations coming from developing countries. The study also found a jump in citations when articles first become openly available from commercial publishers at the end of an embargo period
Attribution of advantage to a particular OA component? Not examined
Study Frandsen TF (2009) The effects of open access on un-published documents: A case study of economics working papers. Journal of Informetrics 3(2): 124-133. http://hprints.org/file/index/docid/352369/filename/OA_advantage_for_WP.pdf
Disciplinary area Economics
Sample Working papers in EconLit, RePEc and ten institutional working paper collections
Basic analytical approach Time elapsed for citations to accrue: Citations to working papers were measured over a period of ten years. Time elapsed for citations to accrue: up to10 years
Filtered out self-citations? No
Citation advantage? No. Found no clear tendency towards an increase in impact during 10 years of open availability for the working papers. Conversely, economics articles in high-impact journals do show a clear tendency for citation impact to increase in a ten-year period. The author therefore deduced that there is no OA citation advantage
Attribution of advantage to a particular OA component? Not examined
Study Gargouri Y & Harnad S (2009) Logistic regression of potential explanatory variables on citation counts. Preprint 11/04/2009.
Disciplinary area Engineering, Biology, biomedicine, chemistry, psychology, mathematics, clinical medicine, health, physics, social sciences, earth sciences
Sample 27,197 articles in total. 6,215 articles from institutions with mandatory OA policies and 20,982 control articles from institutions without such policies (i.e. articles voluntarily made OA by their authors)
Basic analytical approach Compared these OA articles to articles published in the same issue of the same journals that had not been made OA. Analysed by logistic regression. Time elapsed for citations to accrue: 2 to 6 years
Filtered out self-citations? Yes
Citation advantage? Yes, and size of OA advantage varies with discipline. There was no correlation found with mandated or non-mandated status. The advantage found was independent of Journal Impact Factor, time since publication, number of references in the article and number of co-authors. Found that the increase in citations for OA articles is strong for highly-cited articles. Articles from mandated institutions have increased citations in the medium-to-highly cited range. Review articles have increased citations and the effect is greatest in the highly-cited range.
Attribution of advantage to a particular OA component? Confirms other findings that suggest that the best quality (i.e. the most highly-cited) articles have most to gain, relatively, from OA. Also found no evidence to support the Selection Bias, since there was no difference in the citation advantage for mandated articles and non-mandated articles (i.e. that might be preferentially made OA out of choice because their authors thought they were better examples of their work)
Study Gentil-Beccot A, Mele S & Brooks T (2009) Citing and Reading Behavours in High-Energy Physics. How a Community Stopped Worrying about Journals and Learned to Love Repositories. http://arxiv.org/abs/0906.5418
Disciplinary area High energy physics
Sample 286,180 OA articles in three mutually-exclusive sets, all compared with articles in subscription journals
Basic analytical approach Compared citations to three sets of articles made OA with citations to articles published in the same journals but not made OA. The sets were: preprints (pre-peer-review) posted in arXiv and subsequently published in journals; postprints posted in arXiv and subsequently published in journals; articles posted in arXiv and never published in journals. Time elapsed for citations to accrue: from publication over 2 years
Filtered out self-citations? No
Citation advantage? Yes. Found an “immense” [5-fold] citation advantage from Open Access. Also found that 15% of articles have accumulated citations by the time of publication if they are posted to arXiv as preprints. Finally, found that articles made OA in hybrid high energy physics journals had no citation advantage
Attribution of advantage to a particular OA component? Yes, found evidence for the Early Advantage
Study Kousha K & Abdoli M (2009) The citation impact of Open Access Agricultural Research: a comparison between OA and Non-OA publications. World Library And Information Congress: 75th IFLA General Conference and Council, 23-27 August 2009, Milan, Italy. http://conference.ifla.org/past-wlic/2009/101-kousha-en.pdf
Disciplinary area Agricultural sciences
Sample 400 articles published in journals indexed by Web of Science plus 100 OA articles and 100 non-OA articles from journals published by the FAO
Basic analytical approach Compared citations to 400 articles in journals that had also been made OA (identified by using Google and Google Scholar) with those to articles published in those journals only. Time elapsed for citations to accrue: 2 years (basing approach on the Journal Citation Index methodology for calculating Journal Impact factor)
Filtered out self-citations? No
Citation advantage? Yes. Mean citation counts found: 2 for articles published in journals indexed by Web of Science; 4 for articles published in those journals but also made OA. The FAO journal set showed a mean citation rate for OA of 1.74 citations per article versus 0.28 citations for non-OA articles. Concluded that OA is advantageous to individual articles but not to whole journals
Attribution of advantage to a particular OA component? Not examined
Study Lansingh VC & Carter MJ (2009) Does Open Access in Ophthalmology Affect How Articles are Subsequently Cited in Research? Ophthalmology, 116(8): 1425-1431.
Disciplinary area Ophthalmology
Sample 480 OA articles and 415 non-OA control articles, all published in ophthalmology journals
Basic analytical approach Compared citations to articles that were made OA by their authors with those to articles that were not OA in the same set of journals.
Filtered out self-citations? No
Citation advantage? No. Found an increase in mean citations from 11.5 to 15.2 but the advantage correlated with author number, country of publication, language, subject area and funding though not with access
Attribution of advantage to a particular OA component? Not examined
Study Lin S-K (2009) Full Open Access Journals Have Increased Impact Factors (editorial). Molecules, 14(6): 2254-2255. http://www.mdpi.com/1420-3049/14/6/2254/
Disciplinary area Molecular science
Sample Two journals, Molecules and International Journal of Molecular Science, both published by MDPI (Molecular Diversity Preservation International)
Basic analytical approach Looked at the Journal Impact factors after the journals had gone fully OA. Also looked at two other journals from the same publisher, one that experimented briefly with paid-for OA (via article-processing charges) and one that made all its content OA a short time before the experiment. Time elapsed for citations to accrue: 2 years (basing approach on the Journal Citation Index methodology for calculating Journal Impact factor)
Filtered out self-citations? No
Citation advantage? Yes. Reported an increase in Journal Impact Factors after the journals were made fully-OA. All MDPI journals are now fully Open Access
Attribution of advantage to a particular OA component? Not examined
Study Norris M (2009) The citation advantage of open access articles. PhD thesis, Loughborough University http://hdl.handle.net/2134/4089
Disciplinary area Ecology, mathematics, sociology and economics
Sample In Round 1, 4633 articles: in Round 2, 82 economy journals, 21 sociology journals
Basic analytical approach Compared citations to articles in these journals with those also made OA. Identified OA articles by using Google and OAIster. Time elapsed for citations to accrue: 2 to 4 years
Filtered out self-citations? No
Citation advantage? Yes. The mean citation count for OA articles was 9.04 and for non-OA articles 5.76 (see Norris et al 2008). The size of the advantage varied with discipline; sociology showed the greatest OA advantage and ecology the lowest. Correlation with author number and Journal Impact Factor is weak or non-existent
Attribution of advantage to a particular OA component? Not examined
Study Cheng WH & Ren SL (2008) Evolution of open access publishing in Chinese scientific journals. Learned Publishing, 21(2): 140-152. http://www.ingentaconnect.com/content/alpsp/lp/2008/00000021/00000002/art00009
Disciplinary area Medicine, biology, agricultural sciences, chemistry and a set of university-produced journals
Sample 240 Chinese Open Access journals indexed in the Chinese Science & Technology Journal Citation Index. The sample contained 91 fully OA journals and 139 hybrid OA journals
Basic analytical approach Examined citations, immediacy index and Journal Impact Factor for OA journals and non-OA journals in the 4 fields and in the set of university-produced journals. Time elapsed for citations to accrue: 2 years (basing approach on the Journal Citation Index methodology for calculating Journal Impact factor)
Filtered out self-citations? No
Citation advantage? Yes, there was an approximately two-fold increase in citations for OA journals
Attribution of advantage to a particular OA component? Not examined
Study Davis PM, Lewenstein BV, Simon DH, Booth JG & Connolly MJL (2008) Open access publishing, article downloads, and citations: randomised controlled trial. BMJ, 337: a568. http://www.bmj.com/cgi/content/abstract/337/jul31_1/a568
Disciplinary area Physiology
Sample 1619 articles (247 OA and 1372 non-OA)
Basic analytical approach Made a set of articles in 4 issues of 11 American Physiological Society journals OA (randomly picked) and left the rest non-OA. All these journals routinely make all their contents OA after 12 months. Time elapsed for citations to accrue: 12 months
Filtered out self-citations? No
Citation advantage? No. Found that ‘full-text’ downloads increased by 89% with Open Access and ‘PDF’ downloads increased by 42%, but that OA reduced citations by 5%.
Attribution of advantage to a particular OA component? Not examined
Study Frandsen TF (2008) The integration of open access journals in the scholarly communication system: Three science fields. Information Processing & Management, 45(1): 131-141. http://www.hprints.org/hprints-00326285/en/
Disciplinary area Biology, mathematics, pharmacy & pharmacology
Sample 74 biology journals, 25 mathematics journals, 20 pharmacy & pharmacology journals
Basic analytical approach Compared citations from subscription journals to journals that are OA and those that are non-OA. Controlled for self-citation, Journal Impact Factor and sampling dependency. Time elapsed for citations to accrue: 2 years (basing approach on the Journal Citation Index methodology for calculating Journal Impact factor)
Filtered out self-citations? Yes
Citation advantage? No. The effect of OA on citations was neutral in biology and mathematics and negative in pharmacy & pharmacology
Attribution of advantage to a particular OA component? Not examined
Study Gaule P & Maystre N (2008) Getting cited: does open access help? Ecole Polytechnique Fédérale de Lausanne, CEMI-WORKINGPAPER-2008-007, November 2008 and http://scholar.harvard.edu/files/patrickgaule/files/open_access_proofs.pdf
Disciplinary area Biology
Sample 4388 articles published in PNAS over 2 years
Basic analytical approach Compared citations accumulating over time for articles in the journal that had been made OA as a result of authors paying an article-processing fee with those that were not OA. Also looked to see if there was a correlation with article quality by looking at articles that were in the Faculty of 1000 (F1000) dataset. Time elapsed for citations to accrue: from publication over 2 years
Filtered out self-citations? No
Citation advantage? Yes, but the difference was not found to be statistically significant. [Note that PNAS makes its contents open to all at 6 months and to readers in developing countries from the time of publication]
Attribution of advantage to a particular OA component? Selection Bias explains at least a part of the observed OA citation impact
Study Norris M, Oppenheim C & Rowland F (2008) Open Access Citation Rates and Developing Countries. 12th International Conference on Electronic Publishing (ElPub 2008), Toronto, June 25-27, 2008. http://elpub.scix.net/cgi-bin/works/Show?_id=335_elpub2008
Disciplinary area Mathematics
Sample 1158 articles from 16 high-impact journals
Basic analytical approach Used mathematics because it is not covered by any special access schemes for developing countries (e.g. HINARI). Tested the hypothesis that authors in developing countries are the main (or a significant) cause of the Open Access Advantage. Found OA articles via Google and matched them with non-OA counterparts in the same journals. Time elapsed for citations to accrue: 2 to 4 years
Filtered out self-citations? No
Citation advantage? Yes. The study found a “modest difference” in citations to the two groups of articles that came from authors in the developed world (average 3.84 citations to OA articles versus 2.92 to non-OA articles), but a much greater difference for authors from developing countries. The authors of this article state that the sample of authors from developing countries was small and the study needs to be repeated with a larger sample.
Attribution of advantage to a particular OA component? Not examined
Study Norris M, Oppenheim C & Rowland F (2008) The citation advantage of open-access articles. Journal of the American Society for Information Science and Technology, 59(12): 1963-1972. http://hdl.handle.net/2134/4083
Disciplinary area Ecology, applied mathematics, sociology, economics
Sample 4633 articles
Basic analytical approach Compared citations to OA and non-OA articles in these disciplines, using articles published in the same journal. Time elapsed for citations to accrue: 2 to 4 years
Filtered out self-citations? No
Citation advantage? Yes. The mean citation count for OA articles was 9.04 and for non-OA articles it was 5.76
Attribution of advantage to a particular OA component? Not examined
Study Kurtz MJ & Henneken EA (2007) Open Access does not increase citations for research articles from The Astrophysical Journal. http://arxiv.org/abs/0709.0896
Disciplinary area Astronomy
Sample 4271 articles published in the Astrophysical Journal, which was Open Access but then became subscription-access in 1998
Basic analytical approach Compared citations to articles published in the Astrophysical Journal prior to and after 1 January 1998, when the journal switched from Open Access to toll-access. These articles were matched with counterparts that had also been made Open Access by posting in arXiv. Time elapsed for citations to accrue: 9 to 10 years
Filtered out self-citations? No
Citation advantage? Yes. Found that posting in arXiv raised citations two-fold but citations to articles in the journal before and after it switched to subscription access did not change. These authors have previously pointed out that all astronomy researchers have access to all astronomy journals anyway, meaning that the kind of access they have (Open or subscription) makes no difference.
Attribution of advantage to a particular OA component? Posting in arXiv brings a twofold increase in citations, and this is likely to be the Early Access effect
Study Lin SK (2007) Editorial: Non-Open Access and Its Adverse Impact on Molecules. Molecules, 12: 1436-1437. http://www.mdpi.org/molecules/html/12071436.htm
Disciplinary area Molecular science
Sample Two journals, Molecules and International Journal of Molecular Science, both published by MDPI (Molecular Diversity Preservation International)
Basic analytical approach Looked at papers published in 2005 and 2006 under the ‘hybrid OA’ scheme that these journals had at the time. Time elapsed for citations to accrue: 12 to 24 months
Filtered out self-citations? No
Citation advantage? Yes. In that period, the number of OA articles in the journals declined and the journals’ Impact Factor reduced concomitantly. As a result, the publisher has made all articles in these journals Open Access and expects the Journal Impact factors for rise accordingly (see Lin, 2009 for follow-up study)
Attribution of advantage to a particular OA component? Not examined
Study Piwowar HA, Day RS & Fridsma DB (2007) Sharing Detailed Research Data Is Associated with Increased Citation Rate. PLoS ONE, March 21, 2007. http://www.plosone.org/article/fetchArticle.action?articleURI=info:doi/10.1371/journal.pone.0000308
Disciplinary area Clinical trials
Sample Journal articles describing 85 microarray trials
Basic analytical approach Looked at the availability of Open Data supporting the articles to see if this correlated with citation impact. Time elapsed for citations to accrue: 4 to 7 years
Filtered out self-citations? No
Citation advantage? Publicly-available datasets (open data) are significantly associated with a 69% increase in citations to articles that the data accompany. This correlation is independent of Journal Impact Factor, country of authors and time since publication
Attribution of advantage to a particular OA component? Not examined
Study Sotudeh H & Horri A (2007) The citation performance of open access journals: A disciplinary investigation of citation distribution models. Journal of the American Society for Information Science and Technology, 58(13): 2145-2156.
Disciplinary area Various scientific disciplines
Sample ‘Prestigious, pure, stable and long-lasting Open Access journals’ [authors’ descriptions]
Basic analytical approach Unclear
Filtered out self-citations? Unknown
Citation advantage? Unknown. Only the abstract is available except to subscribers to the journal, and the main results and conclusions are not described in the abstract
Attribution of advantage to a particular OA component? Unknown
Study Tonta Y, Ünal Y & A, U (2007) The Research Impact of Open Access Journal Articles. Proceedings ELPUB 2007, the 11th International Conference on Electronic Publishing, Vienna, 13-15 June 2007 http://eprints.rclis.org/9424/
Disciplinary area Biology, economics, physics, mathematics,
chemical engineering, environmental science, sociology,
psychology, anthropology
Sample 270 articles (30 from each discipline)
Basic analytical approach Looked at citations to articles randomly picked from journals listed in the Directory of Open Access Journals. Time elapsed for citations to accrue: 4 to 8 years
Filtered out self-citations? No
Citation advantage? Not measured directly. The study examined whether there is a relationship between OA citation impact and the characteristics of the subject field: that is, is there an OA citation difference between ‘hard, urban’ subjects and ‘soft, rural’ ones. The answer was, not entirely conclusively, no
Attribution of advantage to a particular OA component? Not examined
Study Davis PM & Fromerth MJ (2006) Does the arXiv lead to higher citations and reduced publisher downloads for mathematics articles? Scientometrics, 71(2), May 2007. http://arxiv.org/abs/cs/0603056
Disciplinary area Mathematics
Sample 2765 articles in 4 journals
Basic analytical approach Compared citations to articles in the journals with citations to articles published in those journals but also posted to arXiv. Time elapsed for citations to accrue: 6 months to 8 years
Filtered out self-citations?
Citation advantage? Yes. Mean increase is 35% (number of citations to each article increased from between 0.8 to 2.1, giving a mean increase of 1.1, corresponding to a 35% increase overall)
Attribution of advantage to a particular OA component? Explored Early Advantage and Quality Advantage. The results suggest that the “OA effect may be severely limited to highly-cited articles” i.e. the best articles get the greatest citation benefit. This confirms the Quality Advantage but there is no empirical evidence that this Quality Advantage effect is also a Selective Bias effect (that is, that authors are selectively making their best articles OA) The study found no evidence for Early Advantage
Study Eysenbach G (2006) Citation Advantage of Open Access Articles. PLoS Biology, 4(5), May 2006. http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0040157
Disciplinary area Natural sciences
Sample 1492 articles in PNAS, 212 of which were paid-for Open Access
Basic analytical approach Compared citations to OA and non-OA articles published in PNAS over a period of 6 months. Time elapsed for citations to accrue: 18 months
Filtered out self-citations? No
Citation advantage? Yes. OA articles are 2.1 times more likely to be cited in the first 4-10 months after publication and 2.9 times as likely to be cited 10-16 months after publication
Attribution of advantage to a particular OA component? Not examined specifically
Study Henneken EA, Kurtz MJ, Eichhorn G, Accomazzi A, Grant C, Thompson D & Murray SS (2006) Effect of E-printing on Citation Rates. Astronomy and Physics Journal of Electronic Publishing, 9(2), Summer 2006. http://quod.lib.umich.edu/cgi/t/text/text-idx?c=jep;view=text;rgn=main;idno=3336451.0009.202 and http://arxiv.org/abs/cs/0604061
Disciplinary area Astronomy and physics
Sample All articles published in 2 astronomy and 2 physics journals
Basic analytical approach Tracked citations to these articles over 20 years, covering the periods before and after the arXiv was established. Time elapsed for citations to accrue: from publication over 20 years
Filtered out self-citations? No
Citation advantage? Yes. On average, articles posted on arXiv were ‘cited more than twice as often as those published only in the journals. The study also found that articles in arXiv are read more and cited more
Attribution of advantage to a particular OA component? The authors suggest that the results support their suggestion from previous studies that in physics the best articles are made OA earliest, giving them a significant citation advantage
Study Metcalfe TS (2006) The Citation Impact of Digital Preprint Archives for Solar Physics Papers. Solar Physics, 239(1-2): 549-553. http://arxiv.org/abs/astro-ph/0607079
Disciplinary area Solar physics
Sample 171 articles in the test set and 170 articles in the control set (the control set consists of articles in peer-reviewed conference proceedings
Basic analytical approach Compared OA to non-OA articles. OA articles were made OA either in the arXiv or in Montana State University’s solar physics Open Access archive. Time elapsed for citations to accrue: 2+ years
Filtered out self-citations? No
Citation advantage? Yes. Articles posted to MSU’s archive gained 1.7 times as many citations as non-OA articles and those posted to arXiv received 2.6 times as many citations
Attribution of advantage to a particular OA component? No evidence for Selection Bias. Similar citation boost for conference papers as for journal articles, “suggesting that the higher citation rates are not the result of self-selection of above average papers” [since conference papers are of variable quality]
Study Moed HF (2006) The effect of ‘Open Access’ upon citation impact: An analysis of ArXiv’s Condensed Matter Section. Journal of the American Society for Information Science and Technology, 58(13): 2145-2156. http://arxiv.org/abs/cs.DL/0611060
Disciplinary area Condensed matter physics
Sample 74,521 articles
Basic analytical approach Compared citations to articles posted to arXiv with those to articles in the same journals that were not made available through arXiv Time elapsed for citations to accrue: 12 months to 14 years
Filtered out self-citations? Yes
Citation advantage? The study was not designed specifically to explore whether OA brings extra citation impact but to test the effects of ‘general Open Access’ versus Early Access versus Selection Bias.
Attribution of advantage to a particular OA component? Confirmed the Early Access effect and Selection Bias, but found no ‘general OA ‘effect. Concluded that OA accelerates citations by making articles available earlier rather than by making them freely available
Study Zhang Y (2006) The Effect of Open Access on Citation Impact: A Comparison Study Based on Web Citation Analysis. Libri, 56(3): 133-199. http://www.degruyter.com/view/j/libr.2006.56.issue-3/libr.2006.145/libr.2006.145.xml
Disciplinary area Communication studies (IT)
Sample Two journals, one OA and one not
Basic analytical approach Compared citations for articles in the two journals. Retrieved ‘web citations’ using Google and Yahoo! Time elapsed for citations to accrue: 4-5 years
Filtered out self-citations? No
Citation advantage? Yes, on average Open Access articles received twice the citations of those that are non-OA. The study also identified that the biggest increase in citations came from ‘non-authoritative documents’ (the other two categories were scholarly documents and teaching documents). This category includes more popular literature and professional and practitioner community publications, emphasising the reach of OA and the impact it brings to those constituencies. The study also found a citation boost from authors in developing countries
Attribution of advantage to a particular OA component? Not examined
Study Hajjem C, Harnad S & Gingras Y (2005) Ten-Year Cross-Disciplinary Comparison of the Growth of Open Access and How it Increases Research Citation Impact. IEEE Data Engineering Bulletin, 28(4), December 2005.http://eprints.ecs.soton.ac.uk/11688/
Disciplinary area Ten disciplines:
biology,
psychology, sociology,
health,
political science,
economics,
education,
law,
business,
management
Sample 1,307,038 articles
Basic analytical approach Robot trawled the Web looking for freely-available articles and, when found, matched them with articles from the same issue of the same journal (using the Web of Science database) that were only available in the subscription journal. Time elapsed for citations to accrue: 6 months to 12 years
Filtered out self-citations? Yes
Citation advantage? Yes, Open Access produces a citation increase between 36% and 172%
Attribution of advantage to a particular OA component? Not examined
Study Metcalfe TS (2005) The Rise and Citation Impact of astro-ph in Major Journals. Bulletin of the American Astronomical Society 37(2). http://arxiv.org/abs/astro-ph/0503519
Disciplinary area Astronomy
Sample Around 7000 articles from 13 major astronomy journals
Basic analytical approach Compared citations to articles in 13 astrophysics journals with citations to articles in those journals that had also been made OA by posting in the arXiv. Time elapsed for citations to accrue: tracked citations from publication over 12 years
Filtered out self-citations? No
Citation advantage? Yes, a two-fold difference. And article from higher-impact journals get a proportionately higher boost from being made Open Access by being posted to the arXiv. Higher-impact journal articles not posted to arXiv are cited less often than those from lower-impact journals posted to arXiv.
Attribution of advantage to a particular OA component? Not examined
Study Sahu DK, Gogtay NJ & Bavdekar SB (2005) Effect of open access on citation rates for a small biomedical journal. Fifth International Congress on Peer Review and Biomedical Publication, Chicago, September 16-18, 2005. https://www.researchgate.net/publication/36446808_Effect_of_open_access_on_citation_rates_for_a_small_biomedical_journal
Disciplinary area Medicine
Sample One journal (the Journal of Postgraduate Medicine)
Basic analytical approach Measured citations per volume per year and per 100 articles per year, before and after the journal went Open Access. Time elapsed for citations to accrue: from publication for 15 years
Filtered out self-citations? No
Citation advantage? Yes, between 3 times and 4.5 times.
Attribution of advantage to a particular OA component? Not examined
Study Antelman K (2004) Do Open-Access Articles Have a Greater Research Impact? College and Research Libraries, 65(5): 372-382, September 2004 http://crl.acrl.org/content/65/5/372.short
Disciplinary area Mathematics,
Electrical engineering,
Political science,
Philosophy
Sample 610 articles (mathematics),
506 articles (electrical engineering),
299 articles (political science),
602 articles (philosophy)
Basic analytical approach Compared citations after 2-3 years to articles in ten leading journals in each discipline with citations to articles from those journals that were freely-available on the Web. Time elapsed for citations to accrue: 2+ years
Filtered out self-citations? Yes
Citation advantage? Yes. Increases in citations were:
Mathematics: 91%
Electrical engineering: 51%
Political science: 86%
Philosophy: 45%
Attribution of advantage to a particular OA component? Not examined
Study Harnad S & Brody T (2004) Comparing the impact of open access (OA) vs non-OA articles in the same journals. D-Lib Magazine, 10(6), June. http://www.dlib.org/dlib/june04/harnad/06harnad.html (reporting results from this study: http://opcit.eprints.org/feb19oa/brody-impact.pdf )
Disciplinary area Physics
Sample 95,012 journal articles and conference papers in publication venues indexed by Web of Science
Basic analytical approach Compared articles in physics fields that are openly-available in arXiv with those in the same issues of the same journals that are not Open Access. Time elapsed for citations to accrue:2-12 years
Filtered out self-citations? Yes
Citation advantage? Yes, from 250% to 580% increase.
Attribution of advantage to a particular OA component? Not examined
Study Kurtz MJ, Eichhorn G, Accomazzi A, Grant CS, Demleitner M & Murray SS (2004) The Effect of Use and Access on Citations. Information Processing and Management, 41(6): 1395-1402. http://www.cfa.harvard.edu/~kurtz/IPM-abstract.html
Disciplinary area Astronomy
Sample 2592 articles
Basic analytical approach Used citations from articles in the seven core astrophysics journals to other articles iin those journals. Compared citations to articles published in the journals only with citations to articles published in those journals but also posted to the arXiv (the astro-ph section). Time elapsed for citations to accrue: tracked citations from publication over 20 years
Filtered out self-citations? No
Citation advantage? Yes. Confirmed the Selection Bias and the Early Advantage. Found no general OA Advantage but explained this by saying that all astronomy researchers have access to all the astronomy literature anyway
Attribution of advantage to a particular OA component? Yes, explored (and confirmed) Selection Bias and Early Advantage
Study McVeigh ME (2004) Open Access Journals in the ISI Citation Databases: Analysis of Impact Factors and Citation Patterns. Thomson Scientific, October 2004. http://science.thomsonreuters.com/m/pdfs/openaccesscitations2.pdf
Disciplinary area All natural sciences
Sample 239 journals indexed by Web of Science
Basic analytical approach Compared OA and non-OA journals (not at individual article level). Looked at citations, impact factor and immediacy index. Time elapsed for citations to accrue: 2 years (basing approach on the Journal Citation Index methodology for calculating Journal Impact factor)
Filtered out self-citations? No
Citation advantage? Yes, in physics, engineering, mathematics and medicine. Not in chemistry or life sciences. Found that ‘recent articles [in OA journals] receive a higher percentage of the total citations than recent articles in traditional [subscription access] journals’.
Attribution of advantage to a particular OA component? Not examined
Study Schwarz G & Kennicutt Jr, RC (2004) Demographic and Citation Trends in Astrophysical Journal Papers and Preprints. Bulletin of the American Astronomical Society, 36: 1654-1663. http://arxiv.org/abs/astro-ph/0411275
Disciplinary area Astronomy
Sample 795 articles
Basic analytical approach Methodology essentially as before, comparing articles published in the Astrophysical Journal only to those published there and made available on arXiv as a preprint. Time elapsed for citations to accrue: 1.5 to 3.5 years
Filtered out self-citations? No
Citation advantage? Yes, deposit n arXiv’s astro-ph increases citations twofold. The difference is slightly higher when the article is posted in arXiv at the time of submission to a journal than when posted after peer review.
Attribution of advantage to a particular OA component? No, but results suggest some evidence for the Early Advantage
Study Lawrence S (2001) Free online availability substantially increases a paper’s impact. Nature, 31 May 2001. http://www.nature.com/nature/debates/e-access/Articles/lawrence.html
Disciplinary area Computer science and related areas
Sample 119,924 peer-reviewed conference articles
Basic analytical approach Plotted citation counts against free online availability of papers and showed that freely-available articles are more likely to have high numbers of citations. Time elapsed for citations to accrue: 1-11 years
Filtered out self-citations? Yes
Citation advantage? Yes. The mean increase in citations to OA articles was found to be 157%. For ‘top’ publication venues (conferences) the median increase was 284%.
Attribution of advantage to a particular OA component? Not examined
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