Open access publishing, article downloads, and citations: randomised controlled trial

doi:10.1136/bmj.a568

Published 31 July 2008, doi:10.1136/bmj.a568
Cite this as: BMJ 2008;337:a568

Research

Open access publishing, article downloads, and citations: randomised controlled trial

Philip M Davis, graduate student, researcher¹, Bruce V Lewenstein, professor of science communication¹, Daniel H Simon, assistant professor of economics², James G Booth, professor of statistics³, Mathew J L Connolly, programmer, analyst⁴

¹ Department of Communication, Cornell University, Ithaca, NY 14853, USA, ² Department of Applied Economics and Management, Cornell University, ³ Department of Biological Statistics and Computational Biology, Cornell University, ⁴ Cornell University Library

Correspondence to: P M Davis pmd8@cornell.edu

Objective To measure the effect of free access to the scientificliterature on article downloads and citations.

Design Randomised controlled trial.

Setting 11 journals published by the American PhysiologicalSociety.

Participants 1619 research articles and reviews.

Main outcome measures Article readership (measured as downloadsof full text, PDFs, and abstracts) and number of unique visitors(internet protocol addresses). Citations to articles were gatheredfrom the Institute for Scientific Information after one year.

Interventions Random assignment on online publication of articlespublished in 11 scientific journals to open access (treatment)or subscription access (control).

Results Articles assigned to open access were associated with89% more full text downloads (95% confidence interval 76% to103%), 42% more PDF downloads (32% to 52%), and 23% more uniquevisitors (16% to 30%), but 24% fewer abstract downloads (–29%to –19%) than subscription access articles in the firstsix months after publication. Open access articles were no morelikely to be cited than subscription access articles in thefirst year after publication. Fifty nine per cent of open accessarticles (146 of 247) were cited nine to 12 months after publicationcompared with 63% (859 of 1372) of subscription access articles.Logistic and negative binomial regression analysis of articlecitation counts confirmed no citation advantage for open accessarticles.

Conclusions Open access publishing may reach more readers thansubscription access publishing. No evidence was found of a citationadvantage for open access articles in the first year after publication.The citation advantage from open access reported widely in theliterature may be an artefact of other causes.

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Rapid Responses:

Read all Rapid Responses

Davis et al's 1-year Study of Self-Selection Bias: No Self-Archiving Control, No OA Effect, No Conclusion: Stevan Harnad
bmj.com, 1 Aug 2008 [Full text]
Word is still out: Publication was premature: Gunther Eysenbach
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Reputation for open access: Shafqat Inam
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Who cares for citation advantage?: Nicola Latronico
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Re: Word is still out: Publication was premature: Trish Groves
bmj.com, 2 Aug 2008 [Full text]
Not a Response: A correction on declared interests: Stevan Harnad
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Advantage of randomized experimental design: William H. Walters
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Early-Release Study Needs Both Randomized and Self-Selection Controls: Stevan Harnad
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Internal control variables were present / trial registration: Gunther Eysenbach
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Authors' Response: Philip M. Davis, et al.
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Re: Authors' Response: James E Till
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Open questions for the author / comment on Harnad: Gunther Eysenbach
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Author's Second Response to Eysenbach: Philip M. Davis, et al.
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Access is more important than citation: Giulio Bognolo
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