582 Wu et al. / J Zhejiang Univ Sci B 2008 9(7):582-590 Journal of Zhejiang University SCIENCE B ISSN 1673-1581 (Print); ISSN 1862-1783 (Online) www.zju.edu.cn/jzus; www.springerlink.com E-mail: [email protected] Editorial: On indexing in the Web of Science and predicting journal impact factor Xiu-fang WU1, Qiang FU2, Ronald ROUSSEAU3,4 (1Journals of Zhejiang University SCIENCE (A&B), Zhejiang University Press, Hangzhou 310027, China) (2Zhejiang University Press, Hangzhou 310028, China) (3KHBO-Association K.U. Leuven, Industrial Sciences and Technology, Zeedijk 101-8400 Oostende, Belgium) (4K.U. Leuven, Steunpunt O&O Indicatoren, Dekenstraat 2, B-3000 Leuven, Belgium) E-mail: [email protected]; [email protected]; [email protected] Received Feb. 10, 2008; revision accepted May 20, 2008 Abstract: We discuss what document types account for the calculation of the journal impact factor (JIF) as published in the Journal Citation Reports (JCR). Based on a brief review of articles discussing how to predict JIFs and taking data differences between the Web of Science (WoS) and the JCR into account, we make our own predictions. Using data by cited-reference searching for Thomson Scientific’s WoS, we predict 2007 impact factors (IFs) for several journals, such as Nature, Science, Learned Publishing and some Library and Information Sciences journals. Based on our colleagues’ experiences we expect our predictions to be lower bounds for the official journal impact factors. We explain why it is useful to derive one’s own journal impact factor. Key words: WoS (Web of Science), JCR (Journal Citation Reports), Citation analysis, Predicted impact factors doi:10.1631/jzus.B0840001 Document code: A CLC number: G23; G354 INTRODUCTION result of the establishment of the SCI (Garfield, 2001). The use of the IF as a visibility (quality?) measure is The Science Citation Index (SCI) was launched widespread because, according to (Garfield, 2006), it in 1963 (covering 1961 data) and is widely used as a tends to correspond with scholars’ view of the best tool for the assessment of journals and even individ- journals in their own specialty. ual researchers. If it is to be used appropriately as part The IF has often been criticized as unrepresen- of a scientific research evaluation system by univer- tative or misleading (Rossner et al., 2007). In recent sities, funding organizations or governments, it is of years the number of articles, often editorials, dis- the utmost importance to know and understand the cussing the IF is clearly on the rise (Bar-Ilan, 2008). specific indexing methods underlying this database. Although there are many conflicting opinions about Yet, it is shown that this is not easy to find out. IFs, most people agree that the IF is only a numerical Eugene Garfield introduced the idea of an impact indicator of visibility and is such only weakly related factor in 1955 (Garfield, 1955). This impact factor, to quality. Yet, ‘quality’ itself is a subjective notion. however, referred to articles, not journals, and was not We note that the IF certainly does not reflect the yet clearly defined. No mathematical formula for its quality of the peer review process to which a journal calculation was proposed at that time. Several years subjects submitted articles (Kurmis, 2003; Benítez- later, he and Irving H. Sher created the journal impact Bribiesca, 2002). Some editors seek to understand the factor (JIF). This index was designed for comparing IF calculation so that they can manipulate it to their journals regardless of their size and was a natural journal’s advantage (Jennings, 1998). Citation and Wu et al. / J Zhejiang Univ Sci B 2008 9(7):582-590 583 publication patterns differ between disciplines, so the CONTENTS INDEXED BY THE WoS IF is only meaningful when it is used to compare journals within the same discipline (Testa and A researcher’s scientific attainments will gener- McVeigh, 2004; Moed, 2005). An IF in one subject ally be reflected and judged by his or her academic should never be compared with one in another; the articles. As a journal provides a platform for com- relative ranking of journals within the same area is of munication with its own specific audience, it pub- greater importance, see e.g. (Rousseau and Smeyers, lishes more than just full scientific research papers, 2000) who provided an example where this has been but also editorials, reviews, comments and short notes. done for local assessment of research groups. Great Once a journal is covered by SCI, all items in it will care is needed when using the IF as an evaluation tool be indexed by SCI databases, such as Science Citation (Zhang et al., 2003). Particularly in comprehensive Index-EXPANDED (SCI-E), Social Science Citation universities the evaluation of scientific research arti- Index (SSCI), Index Chemicus (IC), Current Chemi- cles needs special care and should not be based on the cal Reactions-EXPANDED (CCR-E), irrespective of IF of the journal in which the article is published whether the articles appeared in regular issues, sup- (Seglen, 1994). Rousseau (2002) wrote that the qual- plements or special issues. The indexers of the WoS ity of a journal is a multi-faceted notion: a simple IF distinguish the following publication types: Article, can at best catch only one aspect. In this article we Bibliography, Biographical-Item, Book Review, will focus on IFs, not on the Web of Science (WoS) Correction-Addition, Database Review, Discussion, and all its tools. Accuracy of citation counts in general Editorial Material, Excerpt, Hardware Review, Item (hence affecting IF calculations) is discussed in about an Individual, Letter, Meeting Abstract, Meet- Chapter 13 of (Moed, 2005). ing Summary, News Item, Note, Reprint, Review, We recall that the Journal Citation Reports (JCR) Software Review. Some of these, however, are hardly published by Thomson Scientific evaluate and com- used (Meeting Summary is a case in point) and will pare journals using citation data drawn from over not be considered. More types are indexed in the Arts 9100 scholarly and technical journals, and published & Humanities Citation Index, but these too will not be meeting proceedings from more than 3300 publishers considered. in over 60 countries (Journal Citation Reports 4.0, In order to have an idea of the relative amount of 2006). Although impressive, this number falls far publications of each type we searched Thomson short of the estimated total of more than 64000 aca- Scientific’s WoS and summarized all document types demic/scholarly journals in existence, according to indexed On the WoS from 2004~2007, see Table A1 Morris (2007), while Brumback (2008) mentions in Appendix. 40000 journals of which about 15000 deserve to be Document types published and hence indexed called academic. the most are: Article, Meeting Abstract, Editorial Also, we recall the definition of the JIF as used in Material, Review, Letter and News Item. In order to the JCR. Journal J’s IF in the year Y is defined as: the make a distinction between the WoS type Article and ratio of the number of citations received in year Y by ‘just’ an article, the former will always be written in all documents published in journal J in the years Y–1 italic and with a capital A. and Y–2 and the sum of the number of citable docu- ments published in journal J in the years Y–1 and Y–2. The term citable document will be discussed DOCUMENT TYPES AND CITABLE (SOURCE) further in this paper. ITEMS COUNTED IN THE IMPACT FACTOR The first author belongs to the editorial office of CALCULATION Journals of Zhejiang University (A&B), two peer- reviewed journals (Zhang et al., 2003) indexed by Not all indexed items, even those published in Thomson Scientific since 2007 and 2008 respectively, the most famous journals, are the outcome of scien- and publishing almost exclusively substantive re- tific research. For example, parts of Science and Na- search or review articles. It is in this function that we ture are of the (scientific) newspaper type. In these began the investigation reported here. newspaper-type sections, news items, comments, and 584 Wu et al. / J Zhejiang Univ Sci B 2008 9(7):582-590 short reports are published. Such items attract a large mation Science and Library Science, including Libri, audience. Library Journal (Libr J), Scientist, Journal of Li- IF calculation is based on two elements: the brarianship and Information Science (J Libr Inf Sci), numerator, which is the number of citations in the Library & Information Science Research (Libr Inform current year to any items published in a journal in the Sci Res), Library Trends (Libr Trends), Scientomet- previous 2 years, and the denominator, which is the rics, Journal of Documentation (J Doc), Science and number of substantive articles (citable items) pub- Engineering Ethics (Sci Eng Ethics) and Learned lished in the same 2 years (Garfield, 1999). JCR’s Publishing (Learn Publ), trying to find out exactly source data table shows that citable items in the JCR which items are considered as source items. are further divided into Articles (i.e., research articles) For example, in Learned Publishing, the main and Reviews. sections are: guest editorial, editorial, articles, re- Generally speaking, an article is the direct report search articles, letter to the editor, industry develop- of an original research finding; a review consists of an ments, personal views, points of view, essay review, overview, or sometimes a comment, on a certain erratum, case study, book reviews, meeting report, etc. problem by an expert in the field; letters (not letters to Research articles, case study and reports are consid- the editor) carry discussions of scientific problems.