Cost-Benefit Model of Library Acquisitions in Terms of Use: Progress Report

A project has been undertaken to study the use of library materials: to evaluate acquisition decisions in terms of subsequent use and to derive a cost‐benefit model for use in purchasing and resource sharing and in the weeding and retirement of little‐used materials. This first progress report considers only circulating books and monographs. Data derived from circulation records are analyzed in terms of the number of uses per individual item. A surprising result is the nearly straight‐line plot (semi‐log scale) that exhibits consistent halving of the number of items circulated with each successive increase in number of uses. These results are consistent over each of five years studied. The phenomenon is not yet explained. In addition, it is observed that only half of the collection is circulated one or more times over a five‐year period.