Do Download Reports Reliably Measure Journal Usage? Trusting the Fox to Count Your Hens?

Download rates of academic journals have joined citation counts as commonly used indicators of the value of journal subscriptions. While citations reflect worldwide influence, the value of a journal subscription to a single library is more reliably measured by the rate at which it is downloaded by local users. If reported download rates accurately measure local usage, there is a strong case for using them to compare the cost-effectiveness of journal subscriptions. We examine data for nearly 8,000 journals downloaded at the ten universities in the University of California system during a period of six years. We find that controlling for number of articles, publisher, and year of download, the ratio of downloads to citations differs substantially among academic disciplines. After adding academic disciplines to the control variables, there remain substantial “publisher effects”, with some publishers reporting significantly more downloads than would be predicted by the characteristics of their journals. These cross-publisher differences suggest that the currently available download statistics, which are supplied by publishers, are not sufficiently reliable to allow libraries to make subscription decisions based on price and reported downloads, at least without making an adjustment for publisher effects in download reports.