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    Data

    For the period 1988-98, the U.S. Department of Justice collected publisher and price data for some 3000 journals, and holdings information from various libraries. I supplement these data with additional information extracted from the ISI's Journal Performance Indicators database (JPIOD). This database allows me to calculate annual citation rates for individual journals;[12] JPIOD also includes the number of papers published annually by each journal during the sample period.

    My empirical analysis is focused on a subset of these journals, namely, biomedical titles. The reasons for this choice are several. First, based on my discussions with various librarians, biomedical libraries are most likely to evaluate their purchases using the portfolio approach described earlier; furthermore, these libraries typically make no distinctions among various biomedical disciplines, permitting us to consider all biomedical titles as part of a single, large portfolio.[13] Finally, practical considerations, including the fact that biomedical holdings data are reported in a relatively standard fashion, supported an initial focus on this subset of titles.[14]

    During the sample period, almost two thousand ISI-ranked biomedical journals were published; complete time series were available for about 1800 of these titles. Of this latter group, almost 1400 were published by organizations with at least three ISI-ranked titles. For the analysis presented here, only journals sold by commercial firms with portfolios consisting of ten or more titles were considered (thus excluding journals distributed by small private publishers as well as the non-profits), or about 900 titles. Complete holdings data for 194 U.S. medical libraries were collected, representing in aggregate some 60,000 subscriptions to ISI-ranked journals; the libraries were randomly selected from the approximately 1500 Medical Library Association members. Libraries of all sizes are represented in the sample, some holding less than ten subscriptions, while others report collections exceeding 1,300 titles.

    The sample period, 1988-1998, is useful in at least two respects. First, it is sufficiently long to assess whether price increases continue in the journal market. Second, as described above, the period contains a number of natural experiments, i.e., publishing mergers, that enables me to identify the impact of mergers on pricing. Growth via merger should be distinguished from internal growth arising from the introduction of new titles. The latter may produce benefits (such as coverage of emerging fields of study) that helps to offset any intentional competitive harm. Harm associated with acquisitions, on the other hand, is less likely to be balanced by substantial benefits. Journals are simply reshuffled and, based on the public statements made by merging firms, the fixed cost savings seem to be small.[15]