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Graefe`s Arch Clin Exp Ophthalmol (2007) 245:925927 DOI 10.1007/s00417-007-0618-1
EDITORIAL
The delicate topic of the impact factor
B. Kirchhof & N. Bornfeld & F. Grehn
Published online: 12 June 2007 # Springer-Verlag 2007
The definition of the impact factor
In the early 1960s, Irving H. Sher and Eugene Garfield created the journal impact factor (IF) to help select journals for the new Science Citation Index (SCI). They quickly recognised that small journals which specialise in certain topics may not be selected if dependent solely on total publications or citation counts. A simple method was then required for journals, regardless of size or citation frequencythe impact factor [1].
A journals IF is based on two elements: the numerator, which is the number of citations in the current year to any items published in a journal in the previous 2 years, and the denominator, which is the number of substantive articles (source items) published in the same 2 years. Experience has shown that in each specialty the best journals are those in which it is most difficult to have an article accepted, and these are the journals that have a high IF.
The use of the impact factor in research evaluation
Particularly in Germany, as in Austria and in Japan, the IF has developed significant influence beyond its original goal. In these countries, research assessment rests too heavily on the inflated status of the impact factor.
In its original sense, the IF represents a comparative measure of the quality of a journal. The IF simply reflects the ability of journals and editors to attract the best papers available [2]. Hence, the IF stands for the quality of the journal and not for the quality of the individual paper. In practical use in Germany, however, the IF of the journal is taken as a measure for the individual paper. Furthermore, the journals IF is attributed to each author of that specific article, irrespective of the number of authors and the contribution he or she made to this article. The individual citation rate of an author or article is totally neglected in this system.
Despite evident limitations, the IF is very influential. Although even Thomson Scientific acknowledges that the impact factor has grown beyond its control and is being...