Accuracy of indexing coverage information as reported by serials sources

This article reports on the accuracy of indexing service coverage information listed in three serials sources: Ulrich's International Periodicals Directory, SERLINE, and The Serials Directory. The titles studied were randomly selected journals that began publication in either 1981 or 1986. Aggregate results reveal that these serials sources perform at 92%, 97%, and 95% levels of accuracy respectively. When the results are analyzed by specific indexing services by year, the performance scores ranged from 80% to 100%. All three serials sources tend to underreport index coverage. The author advances five recommendations for improving index coverage accuracy and four specific proposals for future research. The results suggest that, for the immediate future, librarians should treat index coverage information reported in these three serials sources with some skepticism.