Prior evidence that downloads predict citations 6 September 2004
Stevan Harnad
and
Tim Brody

BMJ 2004; 329: 2004
Re: Prior evidence that downloads predict citations
http://bmj.bmjjournals.com/cgi/eletters/329/7465/546#73000

Pernbeger's (2004) finding that download counts (what we call "usage impact") of British Medical Journal articles predict citation counts ("citation impact") for those articles in subsequent years confirm what Tim Brody's online usage/citation correlator http://citebase.eprints.org/analysis/correlation.php has been demonstrating for several years now across a number of areas in physics and mathematics ( Brody & Harnad 2004, in prep.): There is a significant correlation between downloads today and citations two years later.

This correlation has two immediate implications:

(1) Download counts can be used as early performance indicators for papers and authors, even before their impact is reflected in citation counts: http://citebase.eprints.org/ ( Hitchcock et al. 2003).

(2) Enhancing usage impact is yet another reason for authors to provide open access to their articles by self-archiving them.
References

Brody, T. & Harnad, S. (2004, in prep.) Using Web Statistics as a predictor of Citation Impact. http://www.ecs.soton.ac.uk/~harnad/Temp/timcorr.doc

Harnad, S. & Brody, T. (2004) Comparing the Impact of Open Access (OA) vs. Non-OA Articles in the Same Journals, D-Lib Magazine 10 (6) June http://www.dlib.org/dlib/june04/harnad/06harnad.html

Hitchcock, Steve; Woukeu, Arouna; Brody, Tim; Carr, Les; Hall, Wendy and Harnad, Stevan. (2003) Evaluating Citebase, an open access Web-based citation-ranked search and impact discovery service http://opcit.eprints.org/evaluation/Citebase-evaluation/evaluation-report.html

Perneger, T.V. (2004) Relation between online "hit counts" and subsequent citations: prospective study of research papers in the BMJ. BMJ 2004;329:546-547 (4 September), doi:10.1136/bmj.329.7465.546 http://bmj.bmjjournals.com/cgi/content/full/329/7465/546