Tim Brody, Stevan Harnad
Abstract: The use of citation counts to assess the impact of research articles is well established. However, the citation impact of an article can only be measured several years after it has been published. As research articles are increasingly accessed through the Web, the number of times an article is downloaded can be instantly recorded and counted. One would expect the number of times an article is read to be related both to the number of times it is cited and to how old the article is. This paper analyses how short-term Web usage impact predicts medium-term citation impact. The physics e-print archive (arXiv.org) is used to test this.
Conclusion: Whereas the significance of citation impact is well established, access of research literature via the Web provides a new metric for measuring the impact of articles - Web download impact. Download impact is useful for at least two reasons:
(1) The portion of download variance that is correlated with citation counts provides an early-days estimate of probable citation impact that can begin to be tracked from the instant an article is made Open Access and that already attains its maximum predictive power after 6 months.
(2) The portion of download variance that is uncorrelated with citation counts provides a second, partly independent estimate of the impact of an article, sensitive to another form of research usage that is not reflected in citations
Journal of the American Society for Information Science and Technology / Volume 57, Issue 8 , Pages 1060 - 1072 / June 6 2006 / DOI: 10.1002/asi.20373