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Posted by pbio on 07 May 2009 at 22:20 GMT

Author: Gunther Eysenbach
Position: Senior Scientist
Institution: Centre for Global eHealth Innovation
Submitted Date: October 29, 2007
Published Date: October 30, 2007
This comment was originally posted as a “Reader Response” on the publication date indicated above. All Reader Responses are now available as comments.

I thank Philip Davis for his excellent observations, although I do not concur with his conclusion that the citation difference is solely the result of quality differentials - rather, it will be a mix of both. There is no question that selection bias is one of the factors confounding the results (which is why I went through considerable lengths to adjust for these, and which is why much of the previous published work on this topic has been discredited). For the final word on this we will indeed have to wait for the results of the ongoing randomized trials in this area. (I am leading a randomized trial funded by the Canadian Institutes of Health Research, and invite any journal publishers or editors with a hybrid or subscription model to contact me to discuss participation). However, for these results to be available we will have to wait a couple of years.
My own analysis show that 26/212 (12.3%) of open access articles from my cohort were featured on the title of PNAS, compared to 106/1280 (8.3%) of non-OA articles. This difference is statistically not significant (Fishers' Exact Test, P=.07). It is unclear whether the statistical models I used were sufficient to adjust for these differences.
The fact that OA articles received more media coverage than non-OA articles is interesting and is in line with my own research findings and anecdotal experiences, both as an author and as an editor of open access and non-open access publications [1]. Apart from the explanation offered by Davis (that this points to a quality differential), there is also the alternative explanation: that open access _facilitates_ media coverage. In fact, I have argued that open access will not only speed up uptake within the scientific community (as measured by citations), but will also facilitate uptake by knowledge endusers (including journalists etc.): "I conclude that the open access advantage really has at least three components: (1) a citation count advantage (as a metric for knowledge uptake within the scientific community), (2) an end user uptake advantage, and (3) a cross-discipline fertilization advantage. (...) All of these advantages are of course the result of greater visibility within and beyond the scientific community.". [1]

1.Eysenbach G. The Open Access Advantage. J Med Internet Res 2006;8(2):e8. URL:

Competing interests declared: Editor of an open access journal and author of open access publications.