In late 2010, I was thinking quite a bit about book use in research libraries. The conventional wisdom was that “no one uses print books anymore” in libraries like mine, and indeed annual data provided by the Association of Research Libraries (ARL) showed a pretty clear decline in book circulations: between 1991 and 2008 (the most recent data available at that time), the number of initial circulations in ARL libraries had fallen by over a quarter. And when I ventured into the book stacks in my own library I usually found them spookily deserted.
But I was haunted by a passing comment a colleague had made to me a few years earlier, noting that the conclusions we draw from library usage data can easily be confounded by changes in the library’s user population. It occurred to me that if we really want to understand what’s happening with regard to library patrons and printed books, we need to take into account the changing nature of our patron base. And the simplest and most consistent change in that population is growth over time: university enrollment tends to grow from year to year.
The question I decided to examine, then, was: how much of the change in individual patron behavior is being hidden by raw circulation data? Clearly, if the size of your patron base is growing while circulation numbers remain the same, that means that the average patron is using the printed collection less; and if the circulation numbers are actually falling while your patron base is growing, that means the average patron is using the library at a more steeply-declining rate than the circulation data suggest.
The way to answer this question is simple, but not easy: you track circulation data for a library along with changes to the size of the patron population, dividing the number of circs by the number of patrons, and watch for trends over time. It’s not a particularly challenging statistical task, but gathering the data for a large number of libraries is a lot of work.
So for several months I spent part of each day gathering circulation and enrollment data for each of the 114 ARL member libraries from the ARL Statistics database. I examined the years 1995-2008, calculating two figures for that period for each library: the total change in raw circulation (number of initial circs), and the change in circulation rate (number of circs per full-time student). I counted only initial circulations rather than total circulations (in order to exclude renewal transactions from the calculation, since the point of the study was to measure how many times the books were used, rather than how intensively). I used enrollment as a proxy for “patron base,” even though I recognize that faculty, staff, and community patrons check out books from the library as well. Since these other populations remain relatively constant in size, and since I was more interested in tracking the shape of the change curve than in knowing its exact distance above the X axis, this seemed like a good compromise.
What I found was sobering: on an aggregate basis, ARL libraries had seen a fairly steady number of initial circulation transactions between 1995 and 2008, with totals hovering between 36 and 40 million. However, during that same period the aggregate circulation rate fell by almost 50% (Figure 1)—a significant change in patron behavior, and one entirely masked by the raw circulation trend.
more at: https://scholarlykitchen.sspnet.org/2017/08/21/less-meets-eye-print-book-use-falling-faster-research-libraries/