Modeling Metrics of Digital Media Use in Public Libraries: Holdings and Circulation Vs. Access and Licensing in Post-Custodial Collections

ABSTRACT Public libraries submit the number of holdings and circulation of items in their collections to their state libraries annually, which in turn report these statistics to the Institute of Museum and Library Services (IMLS) Public Library Survey (PLS). The reported numbers qualify public libraries for federal and state funding. Additionally, the quantity of holdings (traditionally monographs, serials and physical popular media) is often compared to the circulation (number of check-outs) of those items to calculate a cost-per-circulation number. This calculation becomes complicated when a library’s “holdings” become ephemeral due to the nature of digital media and digital licensing models. This article describes several existing metrics for assessing the holdings and circulation of digital assets within both public and academic libraries and argues for the adoption of post-custodial holding metrics used by archives to better represent items available to library patrons, especially those in traditionally underserved demographics.