Consistency of assigned class numbers derived from the Library of Congress classification scheme in university libraries: Issues of collocation and implications for information retrieval in online union catalogs

The level of consistency in the assignment of LCC based class numbers within and across library systems was studied and where variations existed they were examined to determine the reasons for them. A Direct Study of class numbers assigned to a representative sample of 200 titles and their available editions in 52 American library systems was conducted. Also, a questionnaire survey to clarify library classification policies and classification decisions made by catalogers from the library sample based on a week's work was conducted.; The Direct Study showed that under the condition that a library system has a title, the probability of its having the same class number across library systems is (1) greater than 0.85, (2) greater if the title belongs to the sciences than if it belongs to the humanities, which in turn is greater than if it belongs to the social sciences, (3) greater if it is published between 1978-1995, as compared to the period 1972-77, which in turn is greater than if it is published during the period 1911-1971. An examination of titles displaying variation in class numbers among library systems showed that certain titles for example, titles in series, bibliographies and fiction, lend themselves to alternate class numbers. Also it was found that the probability that a title and its available editions will have the same class number across and within the library systems is greater than 0.5. For one-third of the titles displaying non-matches among editions, different class numbers were assigned for different editions by a majority of library systems.; Results of the survey showed that the most frequently cited reason for assigning an original class number for a title is the non-availability of cataloging copy for that title. The Library of Congress supplied record is the most favored copy; libraries tend to accept LC-assigned class numbers without checking them, except in three cases. The assignment of class numbers for three types of titles--titles in series, fiction (PZ vs. PR, PS) and bibliographies--is often guided by internal library policy. There is no uniform policy relating to collocation of editions among those libraries who responded. The tendency seems to be toward assigning class numbers from the copy cataloging record for a recent edition, even if this separates it from its earlier editions.