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Open Access Research and Impact

One aim of the open access movement is to maximize research impact by maximizing research access.

Advocates of the open access movement strongly stress the point that making research openly accessible will increase research productivity and research progress and rewards the researcher or the institution receives (Stevan Harnad). Recent studies examine the connex between open access and impact and argue that open access will lead to maximized impact. The "Lawrence study" has already shown for computer science that papers available online receive remarkably more citations than offline papers.

Analyzing the impact of papers in computer science (mainly conference papers) Lawrence has demonstrated that "on average there are 336% more citations to online articles compared to offline articles published in the same venue" and therefore argues "Articles freely available online are more highly cited. For greater impact and faster scientific progress, authors and publishers should aim to make research easy to access."
Lawrence, S. (2001) Online or Invisible? Nature 411 (6837): 521. http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v411/n6837/full/411521a0_fs.html
(see also http://citeseer.ist.psu.edu/statistics.html)

A follow-up study is under way to validate the effects of the Lawrence study across all disciplines with the help of a 10year ISI sample of 14 million articles. Stevan Harnad reports on that: "The physics analyses up to 2001 are already done, and they reveal even larger effects than those reported by Lawrence, with OA/non-OA citation ratios of 2.5 - 5.8. All indications are that 2002 will raise them even further, as the biggest effects occur within the first 3 years of publication in scientific disciplines (and both OA and the awareness and visibility of OA articles are also increasing yearly)."
Brody, T., Stamerjohanns, H., Harnad, S. Gingras, Y. & Oppenheim, C. (2004) The effect of Open Access on Citation Impact. Presented at: National Policies on Open Access (OA) Provision for University Research Output: an International meeting, Southampton, 19 February 2004. http://opcit.eprints.org/feb19prog.html http://www.ecs.soton.ac.uk/~harnad/Temp/OATAnew.pdf

In contrast, Thomson ISI has conducted a study to compare the citation impact of open access journals (currently 191 out of 8,700 journals covered by ISI are open access). The study found no discernible difference in terms of citation impact or frequency the journal is cited. Nevertheless, ISI states: "Though there is some suggestion in aggregate of a slightly more rapid accumulation of citations, this effect is, so far, minimal. The wide distribution of these OA journals has not yet been shown to have any appreciable effect on their appearance in lists of cited references in other journals." - The results can be found under: http://scientific.thomson.com/ts/media/presentrep/acropdf/impact-oa-journals.pdf

Please note that the study from ISI has a different methodological approach than the other studies as it compares citations from JOURNALS with restricted access to journals with open access whereas the other studies focus on comparing papers which are openly available to papers with restricted access.

Further reading:

Harnad, Stevan; Brody, Tim: Comparing the impact of Open access (OA) vs. non-OA articles in the same journals. D-Lib Magazine, volume 10, number 6 (June 2004). Online available

Information about "the effect of open access and downloads ('hits') on citation impact: a bibliography of studies" can be found here.

Read more about Open Access and the MPS

Last changed: 26 July 2005