Do download reports reliably measure journal usage?  Trusting the fox to count your Hens?

Download rates of academic journals have joined citation rates as commonly used measures of research influence. But in what ways and to what extent do the two measures differ? This paper examines six years of download data for more than five thousand journals subscribed to by the University of California system. While down- load rates of journals are highly correlated with citation rates, the average ratio of downloads to citations varies substantially among academic disciplines. We find that, typically, the ratio of a journal’s downloads to citations depends positively on its im- pact factor. Surprisingly, we find that, controlling for citation rates, number of articles, academic discipline and year of download, there remains a “publisher effect,” with some publishers recording significantly more downloads than would be predicted from char- acteristics of their journals. Download statistics are recorded and supplied to libraries by journal publishers, often subject to confidentiality clauses. If libraries use download statistics to evaluate journals, they may want to account for publisher bias in these statistics