CONTRIBUTIONS to SCIENCE, 5 (1): 63–70 (2009) Institut d’Estudis Catalans, Barcelona DOI: 10.2436/20.7010.01.60 ISSN: 1575-6343 distinguished lectures www.cat-science.cat The evolution of the Science Citation Index* Eugene Garfield** Chairman Emeritus, Thomson Scientific ISI, Philadelphia, Pennsylvania, USA Resum. El Science Citation Index (SCI) va ser proposat fa més Abstract. The Science Citation Index was proposed over 50 de 50 anys per facilitar la disseminació i recuperació de literatu- years ago to facilitate the dissemination and retrieval of scien- ra científica. El seu cercador era únic pel fet de basar-se en una tific literature. Its unique search engine, based on citation recerca per cites, però no va ser àmpliament adoptat fins que searching, was not widely adopted until it was made available va estar disponible en la xarxa en l’any 1972. El Journal Citati- online in 1972. Its by product, Journal Citation Reports, be- on Reports, que apareix com a conseqüència d’aquest en came available in 1975 and included its rankings by impact 1975, incloïa a més una classificació basada en el factor d’im- factor. Impact factors were not widely implemented until about pacte. No era comú utilitzar els factors d’impacte fins a fa una a decade ago, when they began to be used as surrogates for dècada quan van començar a ser usats com una alternativa expected citation frequencies for recently published papers—a per a calcular les freqüències esperades de cites a articles pu- highly controversial application of scientometrics in evaluating blicats recentment—una aplicació molt polèmica de la ciencio- scientists and institutions. Here, the inventor of both the SCI metria com eina per avaluar institucions i científics. L’inventor and its companion, Social Sciences Citation Index, review the de l’SCI, i la seva base de dades companya, l’SSCI, examinarà history of these instruments and discusses their more recent la seva història i discutirà el seu ús més recent en la visualitza- use in graphically visualizing microhistories of scholarly topics. ció gràfica de microhistories de temes acadèmics. Mitjançant In an example thereof, the patented HistCite software for algo- HistCite, un programari patentat per a l’anàlisi historiogràfic al- rithmic historiographic analysis is used to follow the genealogy gorítmic, es parlarà sobre la genealogia del descobriment de of the Watson-Crick discovery of the double-helix structure of Watson-Crick de la estructura de la doble hèlix del DNA i la DNA and its relationship to the work of Heidelberger, Avery, seva relació amb el treball de Heidelberger, Avery i altres. and others. Paraules clau: Science Citation Index · bibliometria · Factor Keywords: Science Citation Index . bibliometrics · Impact d’Impacte Factor Introduction may not remember the role that the early electronic computer played in making it possible for it to appear each week together The Science Citation Index (SCI) was first promulgated in Sci- with its title word indexes and author address directory. In ence in 1955 as an up-to-date tool to facilitate the dissemina- those days, conventional indexes were normally six months to tion and retrieval of scientific literature. As the older generation three years behind the literature, whereas it was estimated that of scientists will remember, an already-existing information ten million worldwide reprint requests were generated each service known as Current Contents was the primordial revolu- year thanks to Current Contents. tionary “idea” that made practical realization of the SCI possi- Nevertheless, the success of the SCI did not come from its ble. Remarkably, Current Contents is still published in print original function as a search engine, but from its subsequent every week although its electronic version has been around for use as an instrument for measuring scientific productivity more than a decade. Even aficionados of Current Contents thanks to its by-product, the SCI Journal Citation Reports (JCR) and its impact factor rankings. The SCI’s multidisciplinary database has two purposes: first, to identify what each scientist has published, and second, * Based on the Lecture given by Eugene Garfield at the Institute for Catalan Studies, Barcelona, on 24 January, 2007. A previous version where and how often the papers by that scientist are cited. of this article was published in International Microbiology 2007, 10:65– Hence, the SCI has always been divided into two author-based 69. parts: the Source Author Index and the Citation Index. By ex- ** Correspondence: Eugene Garfield, Thomson Scientific ISI, Phila- delphia, Pennsylvania (USA). Tel. +1-2152432205. Fax +1-2153871266. tension, one can also determine what each institution and Email: [email protected] country has published and how often the respective papers are 001-128 Contributions 5-1.indd 63 25/11/2009 10:27:07 64 Contrib. Sci. 5 (1), 2009 Garfield cited. This is especially important, since it is remarkable how common. As a result, the explicit citation of earlier relevant difficult it can often be to find a complete list of a particular au- work could not always be found. thor’s publications. Heidelberger was a pioneering molecular biologist; even be- The Web of Science (WoS)—the SCI’s electronic version— fore WWII, together with Oswald T. Avery and others at the links these two functions: an author’s publication can be listed Rockefeller Institute (including Colin M. Macleod and Maclyn by chronology, by journal, or by citation frequency. It also al- McCarthy) he published some primordial work in the history of lows searching for scientists who have published over a given DNA. As a matter of fact, this work is a key link in the genea- period of years. Table 1, for example, shows the resulting list logical history of the Watson-Crick 1953 paper on the double- for a search of scientists who have published for 70–85 years. helix structure of DNA. HistCite was used to track the implicit The record is held by Issac M. Kolthoff, followed by molecular connection between this Watson-Crick paper and the 1944 biologist Michael Heidelberger, whose last paper appeared in work of Avery et al. on pneumococcal DNA. As those familiar 2004, shortly before he died at the age of 104. with the story know and although Jim Watson finally stated a When the SCI was launched in 1964, Irving Sher and I had few years ago that he regretted not having done so, Watson already begun using bibliographic citations to create topologi- and Crick did not cite the 1944 Avery paper in their 1953 pa- cal maps, called historiographs, to investigate whether citation per, since it was rushed into print without the usual reference indexes could aid in writing mini-histories of scientific topics. checks. In order to demonstrate that the significance of Avery’s More recently, the gigabyte memory capacities of computers work was indeed known to contemporary workers, we pro- made it possible to write a program called HistCite—a patent- duced a series of HistCite files by doing an SCI search on the ed software that was in development for about five years and WoS. Then, in order to explore the historical connection be- will be available commercially beginning in February of 2009— tween the work of Heidelberger and his co-author, Oswald Av- which accepts the output of a WoS search and automatically ery, it was essential that the ISI edit thousands of such implicit generates historiographs. By collecting all the relevant cited citations. Figure 1 shows the historiograph created to show papers on a subject in a WoS search, HistCite represents the links between the work of Heidelberger, Avery, and Watson collective memory of the citing authors and produces a visual and Crick. description of the topical history. A key question often arises as Having demonstrated how the WoS search engine can be to the ability of citation indexing to retrieve all the relevant work used to track the historical developments of scientific topics, on a topic. In the pre-WWII days, and much before the advent we can now turn to the subject of the ubiquitous journal impact of molecular biology, citation practices were not nearly as factor. The Annual SCI Journal Citation Reports were officially standardized as they are today, and implicit citation was quite launched in 1975, although we had already been producing Table 1. Scientists who have published for 70 years or more Scientist Birth/Death Publication Years Years published Izaak Maurits (Piet) Kolthoff (analytical chemist) 1894-1993 1917-2002 86 Michael Heidelberger (organic chemist –immunologist) 1888-1991 1909-1993 85 Melvin Guy Mellon ( chemist) 1893-1993 1920-2003 84 Ernst Mayr (biologist) 1904-2005 1923-2005 83 Michel Eugene Chevreul (chemist) 1786-1889 1808-1889 82 Carl S. Marvel (polymer chemist) 1894-1988 1917-1996 80 Joel H. Hildebrand (chemist) 1881-1983 1907-1983 77 Linus Pauling (chemist) 1901-1994 1923-1998 76 John Carew Eccles (neurophysiologist) 1903-1997 1929-1992 74 Donald Coxeter (mathematician) 1907-2003 1930-2001 72 Charles Scott Sherrington (physiologist) 1857-1952 1882-1952 71 Alexander Kossiakoff (engineer) Guided missile expert 1914-2005 1935-2005 71 Hans Albrecht Bethe (physicist) 1906-2005 1934-2004 71 Norman Hackerman (chemist) 1912-2007 1936-2006 71 Michael DeBakey (cardiac surgeon) 1908-2008 1937-2006 70 Gerhard Herzberg (chemist) 1904-1999 1924-1992 69 Herman Mark (polymer chemist) 1895-1992 1922-1990 69 001-128 Contributions 5-1.indd 64 25/11/2009 10:27:07 Evolution of the Science Citation Index Search Engine to the Web of Science Contrib. Sci. 5 (1), 2009 65 guity often causes problems, since it is one thing to use impact 1923 factors to compare journals and quite another to use them to 1924 compare authors.