Impact Factors

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The editors of Epidemiology have suggested that the impact factor does not influence where authors choose to submit papers, based on a before-and-after comparison of the ratio of submissions in the second half of 2011 to those in the first half (impact factors are released in the middle of the year), during which its position in the impact factor league table had improved.1 The analysis was centered around a year with a tiny difference in impact factors among the leading general epidemiology journals (eFigure 1, https://links.lww.com/EDE/A759). We became editors of the International Journal of Epidemiology (IJE) in 20002 and therefore have data on submissions since then. Over that period, the IJE moved from having an impact factor of about half that of EPIDEMIOLOGY and the American Journal of Epidemiology (at that time the two leading general epidemiology journals) to an impact factor 15% and 23% higher, respectively. The Figure presents the impact factor as released in June of each year in relation to the number of submissions in the subsequent 11 months (July of that year to May of the subsequent year) and shows a close relationship, which appears to be more than a simple upward trend. We also tested the hypothesis that the important metric was the impact factor of our journal—initially lower and now higher—compared with the average of Epidemiology and the American Journal of Epidemiology shown in eFigure 2 (https://links.lww.com/EDE/A759), which reveals much the same pattern. We think this long-term monitoring is likely to give a more valid interpretation of the effects of the impact factor on authors’ behavior.FIGURE: The number of submissions to the IJE in relation to the impact factor.Impact factors are highly problematic indicators of the value of material published in journals, as has been widely discussed.3,4 We are in no way arguing that it is in the best interests of the discipline for authors to choose journals on the basis of the impact factor. However, as long as some evaluations of academic merit and funding are based on this metric, it is likely to influence authors’ behavior with respect to where papers are submitted. George Davey Smith Barbara Coatesworth Jane Ferrie International Journal of Epidemiology Editorial Office School of Social and Community Medicine University of Bristol Bristol, United Kingdom [email protected] Shah Ebrahim International Journal of Epidemiology Editorial Office School of Social and Community Medicine University of Bristol Bristol, United Kingdom London School of Hygiene and Tropical Medicine London, United Kingdom