Journal Citation Reports

JOURNAL CITATION REPORTS Introduction ]eyond the basic discipline, as interdisciplinad I. journals, References, md multidisciplinary ‘mission-oriented’ research requires broader journal coverage, the relevatrrx and Citations md usefulness of journals outside the disciplin- my core may be difficult to determine. Even A citation index is baaed on the principle that within the small d~ciplinary or departmental li- there is some meaningful relationship between brary, when a choice between journals is dictated one paper and some other that it cites or that by restricted acquisitions budgets, considerations cites it, and thus between the work of the two less relevant than scientific merit may all too authors or two groups of authors who published likely determine or force the choice--politics, the papers. sheer habit, relative subscription cost, and so on. The entire SC/Q data base is stored on mag- Thus, the Journal Citation Reporma (JCR” ) netic tape, and it is thus amenable to extensive extends the use of citation analysis to examine manipulation and analysis. In the case of au- the relationships among journals rather than thors, we have been able to identify the fre- among articles and their authors. The JCR an- quency with which they and their papers are swers these basic questions: how often has a cited in the literature, over any chosen time journal been cited? what journals have cited it? period. Counts of this sort are strictly quantita- how frequently have particular joirrnah cited it? tive and objective. But even admitting this limi- does the cited material in the case of a particular tation, an author’s or a paper’s frequency of IOUrnal come primarily from older articles, newer citation has been found to correlate well with articles, or does the citation pattern show a professional standing. It is certainly not the on/y chronological consistency? what journals has the measure, nor one that can be used, for any particular journal itself cited? how often has it purpose, in isolation. We do not claim for it the cited each of them? is it citing old material, new absolute reliability that critics of citation analysis material? what part of these counts is due to have wrongly imputed to us when they have self-citation? in other words: who uses a partic- attacked it. The fact does remain, however, that ular journal? how frequently? for what purposes? it provides a useful objective criterion previously unavailable. The Total Framework Basically the same principle can be used in Like any other tool, the JCR cannot be used evaluation of journals, rather than of authors’ indiscriminately. It is a source of highly valuable publications or single papers. When a scientist information, but that information must be used cites a previously published article, he tells us, in within a total framework proper to the decision to a sense, that he has read it and has some reason be made, the hypothesis to be examined, and for bringing it to our attention. The more fre- rarely in isolation without consideration of other quently a journal’s articles are cited. the more factors, objective and subjective. For example, the world’s scientific community implies that it there are undoubtedly highly useful journals that finds the journal to be a carrier of useful infor- are not cited frequently. Scientists read many mation. such journals for the same reason people read newspapers and other non-scientific periodicals-- Evsfuaring Journals to keep up with what’s going on generally. They It has always been and still remains diftlcult to may rarely cite such journals in their published assess the relative importance of scientific and work. This does not mean that such uncited or technical journals. There have been few, if any, infrequently cited joumala are any less useful for totally objective criteria by which to measure their intended purpose than cited journals. h them. Researchers and their library colleagues does mean, however, that these journals are quickly learn what journals are most ‘important’ written and read for a purpose other than the for particular dkciplines, and countless studies communication of original research fmtlngs and have been carried out to establish ‘core-journal’ the indispensable summary of research findings lists. But as research interest and activity extend provided by reviews. 558 Another consideration is that citation frequen- say, citations of only 35 dlflerent articles. The 35 cy is sometimes--indeed to some extent must different cited articles appeared in 10 different be--a function of variables other than scientific journals. In other words, the 40 references cited merit. Some such variables may be an author’s some articles--at the most S--more than Onm, reputation, the controversiality of subject matter, and cited each of the ten different journals an a journal’s circulation and its cost, reprint dis- average of 4 times. In compiling the JCR. it is semination, its coverage by current-awareness the number of different article-to-article links and indexing and abstracting services, society that is counted. In this case the Journal of rhe memberships, the availability and estent of li- American Chemical Society k credited with 35 braries’ journal collections, national research pri- unique references. Their 35 citations will be dis- orit ies. tributed among the 10 different cited journals, each receiving on the average a ‘cited’ count of Compiking Joumsf Data 3.5--not 4. and not 1. Lest this point be passed over as a laboring of The ./CR’”analyzes and summarizes a massive the obvious, the user must remain aware that the amount of data: the 1975 listings are based on JCR represents only one of several possible de- 5,395310 citations from the references of ap scriptions of journal relationships. Others have proximately 420,000 source items published in been suggested above, namely, one based on 1975 issues of some 2500 SCl source purnals. data incfuding duplicate citation links between Obviously, it will be easier to use information the same two articles, and another based on data from the .lCR if one understands how it has been including only unique joumaf links rather than compiled. The user must remember that the JCR unique article links between the same two arti- is a calendar-year report, cwmpiled from the cles. Science Citation Inde.-& (SCP ) data base. The SC1 indicates the reference/citation ]inks The Ever-Changing River between an article published during the year and of Journals all previously published articles cited in the cur- Many users will need no reminder that the rent article’s references. The SC/ identifies every management of serials, among which are in. unique link between any cited article and all arti- eluded scientific journals, is one of the thorniest cles that have cited it during the year, supplying thickets of bibliography and librarianship. Even authors’ names, journal titles, journal volume knowledgeable estimates of the number of extant and page numbers. and year of publication. The scientific and technical periodicals vary so JCR extracts from each of these unique citation widely--by tens of thousands--that the uninitiated links four pieces of information: two journal titles cannot be blamed for doubting the competence of and two publication years. One of the extracted those concerned with the problem. journal titles is that in which the current citing Like a real river, the river of scientific and article was published. The other journal title is technical publication is ever-changing. Its ele- that in which the cited article was published. One ments are complex, its cuurse confusing, but of the publication years is that in which the cur- werall the difficulties and problems of serials rent citing article was published. Since the JCR hbrarianship in science are a reflection of the is a calendar-year compilation, this year date will strength and be the same in all cases. The other publication force of its river’s progress. Jour- by year will be the year in which the cited article nals die but are replaced others: journals split into sections was published. Brow,and (letteredor num- In this extraction process many similar links beredor subtitledand resubtitled),or into new are generated from the millions of different and ioumals;journalsmay narrowtheir interestand journals under old or new unique links identified fully in the SC1. The JCR merge with other titles; titles change to reflect a reorientation even counts how many of these similar links there now when splitting and merging is avoided--a few are, and tabulates the results in its two ‘detail’ words are added, some dropped, the language of listings, first by citing journal and then by cited journal. the title itself may change. This characteristic but vital inconstancy of scientific publication is severely problematic for an Article-to-Articfe Links effort like the JC#’that seeks to describe journal h is important to remember the way these relationships over periods of time. There is, to be counts have been generated, as described above. sure, the additional confusion contributed by in- They are counts of referencdcitation links, not correct or ambiguous citations, by the sometimes counts of articles, nor of journals per se. For ex- truly stultifying virtuosity of title abbreviators, ample, a 1975 article published in Journal of the by the ‘separateness’ of original and translated American Chemical Society may have had 40 re- versions of the same journal, etc. As irritating ferences. These 40 references contained, let us and time-wasting as such things are, they are 559 nevertheless of relatively minor significance n one field, but because of other dissemination within the total complex framework. Most are n others a redundancy. Citation practices differ amenable to easy solution, given persistence, ‘rorrrone field to another, The d~fference may be generous computer time, and the ability to sur- implicated by a difference in the half-life of vive seemingly endless deserts of boredom.

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