Abstract
Impact factors are currently the bibliometric index most used for evaluating scientific journals. However, the way in which they are used, for instance concerning the study or journal types analyzed, can markedly interfere with estimate reliability. This study aimed to analyze the citation distribution pattern in three Brazilian journals of general medicine. This was a descriptive study based on numbers of citations of scientific studies published by three Brazilian journals of general medicine. The journals analyzed were São Paulo Medical Journal, Clinics and Revista da Associação Médica Brasileira. This survey used data available from the Institute for Scientific Information (ISI) platform, from which the total number of papers published in each journal in 2007-2008 and the number of citations of these papers in 2009 were obtained. From these data, the citation distribution was derived and journal impact factors (average number of citations) were estimated. These factors were then compared with those directly available from the ISI Journal of Citation Reports (JCR). Respectively, 134, 203 and 192 papers were published by these journals during the period analyzed. The observed citation distributions were highly skewed, such that many papers had few citations and a small percentage had many citations. It was not possible to identify any specific pattern for the most cited papers or to exactly reproduce the JCR impact factors. Use of measures like "impact factors", which characterize citations through averages, does not adequately represent the citation distribution in the journals analyzed.
Highlights
Impact factors (IFs) are currently the bibliometric index most used for evaluating scientific journals
For the São Paulo Medical Journal, 134 articles and 100 citations could be identified via Institute for Scientific Information (ISI) (IF = 0.746) versus 134 and 96 from direct search (IF = 0.72)
For Clinics, 203 papers and 324 citations were found via ISI (IF = 1.596), while 203 papers and 288 citations were found from direct search (IF = 1.40)
Summary
Impact factors (IFs) are currently the bibliometric index most used for evaluating scientific journals. This index is defined as the average number of citations received by the papers published in a journal, according to appropriately defined “time windows” (usually two years).[1,2] They were originally developed by E. Widely used, the validity of IFs has been criticized, for example because of problems in defining them or in making comparisons between research fields and paper types.[3,4,5,6] Another point of contention concerns their definition as averages, in a context in which medians would probably be a more adequate statistical index.[7] On the other hand, few studies have tried to empirically assess the behavioral profile of published papers in scientific journals
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