Nature 411, 522 : 31 May 2001

Impact factors, and why they won't go away
Eugene Garfield
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Sir - Brunstein in Correspondence1 asks whether online publishing will herald the end of impact factors. Unless he is forecasting the end of print publications altogether, this is doubtful. Were print journals to disappear, however, I am confident that a new impact factor would be invented. Information scientists are already computing web impact factors2. It would be more relevant to use the actual impact (citation frequency) of individual papers in evaluating the work of individual scientists rather than using the journal impact factor as a surrogate. The latter practice is fraught with difficulties, as Seglen and others have pointed out3. As long as scientists publish articles containing lists of cited references, it will be possible to calculate impact factors. It is to be hoped that citation practices on the web will become sufficiently standardized to permit accurate calculations. It will be necessary to distinguish between citations to URLs for research articles, on the one hand, and, on the other, to readerships as reflected in 'webometric' studies measuring web activity. One ordinarily assumes that there are many more readers than citers, but there is a widespread mythology that authors are cited more than they are read! Eugene Garfield Institute for Scientific Information, 3501 Market Street, Philadelphia, Pennsylvania 19104, USA  These letters form part of Nature's current debate on access to the scientific literature. For more examples, see

1. back to text  Brunstein, J. Nature 403, 478 (2000). |  PubMed
2. back to text  Bjorneborn, L. & Ingwersen, P. Scientometrics 50 (1), 65-82 (2001).
3. back to text  Seglen, P. O. Br. Med. J. 314, 498-502 (1997).

Eugene Garfield, Ph.D.
Chairman Emeritus
Institute for Scientific Information
3501 Market Street
Philadelphia, PA 19104

Letter from John Brunstein

03 February 2000
Nature 403, 478 (2000) © Macmillan Publishers Ltd.
End of impact factors?

Sir Does the expansion of the Internet and journals' online publishing strategies herald the end of 'impact factors'? Many scientific publications now have online versions, often freely available. As Internet access is pervasive (and increasing), busy scientists can now sit with their morning coffee and use a computer search engine to look for articles in their narrow area of interest. The computer database can be much more exhaustive, user-friendly and up-to-date than its old-fashioned paper counterpart. As a result, the researcher can now in effect have a customized 'table of contents' generated on demand.

The overall effect of this practice seems likely to be a shift in reader emphasis away from particular ('high-impact') journals as reference sources, and an increasing importance of specific articles, rather than the journal in which they are published. If this is indeed the case, continued emphasis on 'impact factors' as currently calculated would seem to be misguided, and the concept will need to be redefined.

John Brunstein
Department of Virology, Haartman Institute, University of Helsinki, Haartmaninkatu 3, 00290 Helsinki, Finland