Duplicate Records in WorldCat for 20th-Century American, British, and Canadian Books: A Comparison of Duplication Rates and Causes

The bibliographic record duplication rates in WorldCat for 20th-century books cataloged in English and published in New York, London, and Montreal were estimated by sampling records created by Concordia University. Duplicate sets were identified according to OCLC WorldCat record merging guidelines. New York and London records had similar duplication rates, higher than those for Montreal. Changing descriptive cataloging standards, brief cataloging, and both typographical and MARC coding errors caused failures in duplicate record detection. Records for editions, reproductions, fine arts titles, and conference publications were particularly problematic. The earlier cataloging standards were reviewed to uncover how differences have caused duplicates.