A critical assessment of the impact factor

Abstract

Professional scientific societies are under increasing pressure from medical faculties and other institutions to prepare and justify well-founded assessment scales for publications in their fields. This development will also be relevant for general practice in the process of academic acknowledgement. After presenting various literature and publication indices, the authors critically examine the impact factor, which has been controversially discussed by medical faculties and scientists. The impact factor of a journal (basically the number of times published articles are cited, divided by the number of articles that could theoretically be cited) is calculated annually by the Institute for Scientific Information in Philadelphia and published in the Science Citation Index. Impact factors are biased towards US journals, heavily distorted by speciality and vulnerable to technical problems. Although we conclude that they should not be used in research assessment (especially not to measure the performance of individual scientists), we emphasise the necessity of establishing criteria for assessing the quality of papers and journals alike.