Looking for the Impact of Open Access on Interlibrary Loan

The purpose of this paper is to analyze interlibrary loan (ILL) article requests for evidence of a decrease that could be attributed to the spread of open access. The authors collected and analyzed the interlibrary loan data of two Indiana academic libraries for requests submitted during October and November (peak ILL months) from 2006-2015. The requests were assigned to one of four categories: general, humanities, social sciences, and sciences based on Library of Congress classification, and the relative age of each article was calculated, where the relative age is the difference between year of publication and year of request. Assuming an embargo period of 12-18 months for traditional publications, a change in articles of relative age 0-2 would suggest that scholars were obtaining that material from other sources. The authors then looked for trends that might indicate the impact of open access on interlibrary loan requests. This paper will present the results and discuss the other environmental factors that may influence the number of requests placed within a field of study.