Academic journal article Library Resources & Technical Services

From the Ubiquitous to the Nonexistent: A Demographic Study of OCLC WorldCat

Academic journal article Library Resources & Technical Services

From the Ubiquitous to the Nonexistent: A Demographic Study of OCLC WorldCat

Article excerpt

Analysis of a random sample of bibliographic records from OCLC WorldCat finds that the great majority of items in WorldCat are held by very few participating libraries, and that an inverse geometric relationship exists between the number of libraries holding an item and the number of items with a given level of shared holdings. The findings provide a context for interpreting holding levels in WorldCat with regard to the proportion of widely shared items and the characteristics of items at various ranges of holdings. Used with other quantitative and evaluative measures, these findings will assist libraries in assessing their collections.


OCLC WorldCat is arguably one of the most valuable tools available to librarians, as it provides online, global access to the shared records of thousands of libraries around the world. This enables librarians, at a minimum, to verify the existence of an item mentioned by a patron and to provide correct bibliographical facts of publication for it. More generally, it helps librarians identify and locate items that may not be held in their own collections.

WorldCat is also a potentially powerful research tool for collection analysis because each of its bibliographic records indicates the number of member libraries holding that item. These data are tantalizingly provocative to scholars interested in patterns in the distribution of books, knowledge, and information.

The theoretical basis for considering WorldCat holding levels in library research is that the number of libraries holding a given title provides a score that can measure that title's influence or impact. Several studies conducted over the years on specific library material domains adult fiction, books from small publishers, scientific journals, and award-winning monographic titles in the social sciences and humanities--have cited figures on holdings in WorldCat or its predecessor, the OCLC Online Union Catalog. (1) Similarly, Mirwis has included WorldCat holdings as one of several factors used to rate and rank encyclopedias. (2)

The difficulty with citing these holdings data lies in knowing how to interpret them. Without a clear picture of what exactly is in WorldCat and what the spectrum of distribution is, the raw holdings numbers mean little. Only by examining a sample of items from WorldCat itself, rather than beginning with particular known items or a particular library collection, can one develop an interpretive framework that could maximize the analytical value of these data.

In the interest of providing a context for interpreting WorldCat holding levels, I undertook what might be called a demographic study of WorldCat, focusing on its composition and major characteristics as a population by analyzing a random sample of 500 records. The goal in investigating the items of WorldCat as representatives of a population was to determine the categories of materials that are represented in WorldCat and their proportions, the proportion of widely held items, and the characteristics of those items.

Precedents for this study may be found in publications by White and Perrault. (3) White demonstrated the connection between Research Libraries Group (RLG) Conspectus levels and OCLC holding levels. He found that titles at the research level had holding levels up to 150, and that the midpoint of holdings of titles in library collections at all levels was about 400. (4) Perrault studied a systematic random sample of nearly 3.4 million WorldCat records to gauge trends in library collection building over time and assess WorldCat's potential for promoting shared access to scarce resources. (5) While her study did not concern levels of shared holding in a manner comparable to White's work, she did uncover a finding that is striking when considered alongside White's results: more than 53 percent of the records in Perrault's sample were held by only one member library. (6)

The present study attempts to show the big picture of what is in WorldCat by considering its widely shared items against the background of a much larger number of extremely scarce items. …

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