The decline of subject searching: Long-term trends and patterns of index use in an online catalog

Search index usage in a large university online catalog system over a six-year period (representing about 15.3 million searches) was investigated using transaction monitor data. Mathematical models of trends and patterns in the data were developed and tested using regression techniques. The results of the analyses show a consistent decline in the frequency of subject index use by online catalog users, with a corresponding increase in the frequency of title keyword searching. Significant annual patterns in index usage were also identified. Analysis of the transaction data, and related previous studies of online catalog users, suggest a number of factors contributing to the decline in subject search frequency. Chief among these factors are user difficulties in formulating subject queries with Library of Congress Subject Headings, leading to search failure, and the problem of “information overload” as database size increases. This article presents the models and results of the transaction log analysis, discusses the underlying problems with subject searching contributing to the observed decline, and reviews some proposed improvements to online catalog systems to aid in overcoming these problems. © 1991 John Wiley & Sons, Inc.