News Release

New evidence of the power of open access

Peer-Reviewed Publication


New findings settle one of the arguments about Open Access (OA) research publications: Are they more likely to be cited because they were made OA, or were they made OA because they were more likely to be cited?

The study, which will be published in PLoS ONE on the first day of Open Access Week (18 October), was carried out by a bi-national team of researchers from the University of Southampton's School of Electronics and Computer Science (ECS) in the UK and l'Université du Québec à Montréal in Canada.

The results show that the OA citation impact advantage is just as great when OA is mandatory (i.e., the author's institution or funder requires the author to make all research publications OA) as it is when OA is optional (i.e., the author self-selects whether and what to make OA).

"It is now well-known that those research findings that are made accessible free for all on the Web are more likely to be used and cited than research findings that are accessible only to paid subscribers," said Professor Stevan Harnad at ECS, part of the team who carried out the study. "But we need to ask whether research is more likely to be used and cited because it has been made OA? Or is it made OA because it is more likely to be used and cited?"

According to the "self-selection bias" hypothesis, the greater impact of OA articles is just an artifact of a bias on the part of authors toward selectively making their better -- hence more useable and citeable articles - OA. If the OA impact advantage is just a self-selection bias, then it is far less urgent and important to make all research OA.

The team tested this by analysing all articles that were made OA at the four first institutions in the world to make OA mandatory -- University of Southampton School of Electronics and Computer Science, the first, in 2003, and CERN, University of Minho, and Queensland University of Technology, in 2004 - and comparing their citation impact with control articles, in the very same journals and years, from unmandated institutions, that were made OA by author self-selection or not made OA at all. The OA impact advantage turned out to be just as great, regardless of whether the OA was self-selected or required.

The study also found that the percentage of an institution's yearly research output that is made OA self-selectively varies between 5% and 25%, whereas the percentage when OA is mandated jumps to 60% and climbs toward 100% within a few years of mandate adoption.

The conclusion of the study is hence not only that the OA impact advantage is real, and caused by the greater accessibility of OA articles, but that OA mandates are also the way to make all research benefit from the greater likelihood of being used and cited that OA provides.

Commenting on these new findings, Professor Dame Wendy Hall, a committed advocate of OA said: "This is further convincing evidence that we can all increase the impact of our research by ensuring - through Open Access - that it is available to everyone. If we are to begin to solve some of the really pressing issues facing the planet at the moment we need to be able to draw on all the research insights from many different disciplines and from all the world's research institutions."


Citation: Gargouri Y, Hajjem C, Larivie`re V, Gingras Y, Carr L, et al. (2010) Self-Selected or Mandated, Open Access Increases Citation Impact for Higher Quality Research. PLoS ONE 5(10): e13636. doi:10.1371/journal.pone.0013636

Funding Statement: Social Science and Humanities Research Council, Monitoring, Measuring and Maximizing Research Impact, and Canada Research Chair in Cognitive Sciences. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interest from the authors: The authors have declared that no competing interests exist.

Competing Interest Statement from PLoS ONE: PLoS is a publisher of Open Access journals and hence could benefit from any study which demonstrates an 'OA Citation Advantage'. However PLoS had no involvement in the research presented in this paper. As to the acceptance of any paper in PLoS ONE, this is always at the discretion of the individual academic editor involved, who is not subject to any influence from the publisher.


Prof. Stevan Harnad, Founder and Moderator, American Scientist Open Access Forum, School of Electronics and Computer Science, University of Southampton, Tel: 023 8059 4479, email:

Joyce Lewis, Communications Manager, School of Electronics and Computer Science, University of Southampton (tel. 023 8059 5453; email



Notes to Editors:

1. For information about ROARMAP (Registry of Open Access Materials Archiving Policies) visit:

2. With around 500 researchers, and 900 undergraduate students, the School of Electronics and Computer Science at Southampton is one of the world's largest and most successful integrated research groupings, covering Computer Science, Software Engineering, Electronics, Electrical Engineering, and IT in Organisations. ECS has unrivalled depth and breadth of expertise in world-leading research, new developments and their applications.

3. The University of Southampton is a leading UK teaching and research institution with a global reputation for research and scholarship across a wide range of subjects in engineering, science, social sciences, health, arts and humanities.

4. With over 22,000 students, around 5000 staff, and an annual turnover of almost £400 million, the University of Southampton is one of the country's top institutions for engineering, computer science and medicine. We combine academic excellence with an innovative and entrepreneurial approach to research, supporting a culture that engages and challenges students and staff in their pursuit of learning.

5. The University is also home to a number of world-leading research centres, including the National Oceanography Centre, Southampton, the Institute of Sound and Vibration Research, the Optoelectronics Research Centre, the Centre for the Developmental Origins of Health and Disease, and the Southampton Statistical Sciences Research Institute.

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