Open Access News

News from the open access movement

Friday, September 08, 2006

Questioning the OA impact advantage

Henk F. Moed, New developments in citation analysis and research evaluation, Information Services and Use 26, 2 (2006) pp. 135-137.  (Thanks to Wouter Gerritsma.)

The core of this contribution presents preliminary results from a study examining the effect of “open access” upon citation impact and visibility. This contribution presents the main lines of the research and preliminary findings. Detailed findings from all studies will be published in separate, future research articles....

Following the work by Kurtz et al. and Davis and Fromerth, three effects were distinguished. The first is the genuine Open Access Effect, in the sense that the archive increases access to research papers. The second is termed the Early View Effect: articles appear earlier in the archive than they do in the publisher archive. Finally there is a Self-Selection or Quality Bias Effect. Better authors use the archive, or authors deposit their better papers in the archive. Following Harnad and Brody, the average citation impact of WoS papers deposited in ArXiv was compared to that of articles not deposited in that archive, by calculating an ArXiv Impact Differential.

A preliminary analysis related to a set of 22 WoS journals, in which Physical Review B contributes by far the largest number of papers deposited in ArXiv. Large differences in the ArXiv Impact Differential were found across journals. Moreover, the analysis provided evidence of strong Self-Selection and Early View Effects. Correcting for these effects, the remaining ArXiv Impact Differential may be one or even two orders of magnitude (i.e. factors of 10) lower than the Impact Differentials reported by Harnad and Brody, depending upon journal, citation type and time window, and type of statistic calculated. Whether the remaining ArXiv Impact Differential reflects an open access effect or still a Self-Selection Effect, – the tendency that authors deposit their better papers in ArXiv –, is still an open question....