Journal Citation Reports

Journal Citation Reports (JCR) is an annual publication by the Institute of Scientific Information, a division of Thomson Scientific. It provides information about academic journals in the sciences and social sciences. It was originally published as a part of Science Citation Index, and is compiled from the citation data found there.

Basic journal information
The information given for each journal includes:
 * the basic bibliographic information of publisher, title abbreviation, language, ISSN
 * the subject categories (there are 171 such categories in the sciences and 54 in the social sciences)

Citation information

 * Basic citation data:
 * the number of articles published during that year and
 * the number of times the articles in the journal were cited during the year by later articles in itself and other journals,
 * detailed tables showing
 * the number of times the articles in the journal were cited during the year by later articles in itself and other journals,
 * the number of citations made from articles published in the journal that year to it and other specific individual journals during each of the most recent ten years (the 20 journals most cited are included)
 * the number of times articles published in the journal during each of the most recent 10 years were cited by individual specific journals during the year (the twenty journals with the greatest number of citation are given)
 * and several measures derived from these data:
 * the journal impact factor, the ratio of the number of citations to the previous 2 years of the journal divided by the number of articles in those years — this is essentially the average number of recent citations per article
 * the journal immediacy index, the number of citations that year to articles published the same year,
 * the journal citing half life, the median age of the articles that were cited by the articles published in the journal that year,
 * the journal cited half life, the median age of the articles in the journal that were cited by other journals during the year.

There are separate editions for the sciences and the social sciences; the science portion includes 6166 journals, and the social science edition contains 1,768 titles. The issue for each year is published the following year, after the citations for the year have been published and the information processed. The publication is available online (JCR on the Web), or in CD format (JCR on CD-ROM); it was originally published in print, with the detailed tables on microfiche.

Criticism
The use of these data has been subject to various criticisms, which are discussed in detail in the article on impact factors. The primary acknowledged limitation is that almost all the journals covered are English language journals from western Europe and the United States, and that the information in the derived tables combines original research journals and review journals — which have very different citation behavior.