Journal of the Royal Society of Medicine
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(1) To analyse trends in the journal impact factor (IF) of seven general medical journals (Ann Intern Med, BMJ, CMAJ, JAMA, Lancet, Med J Aust and N Engl J Med) over 12 years; and (2) to ascertain the views of these journals' past and present Editors on factors that had affected their journals' IFs during their tenure, including direct editorial policies. ⋯ IFs of the journals studied rose in the 12-year period due to rising numerators and/or falling denominators, to varying extents. Journal Editors perceived that this occurred for various reasons, including deliberate editorial practices. The vulnerability of the IF to editorial manipulation and Editors' dissatisfaction with it as the sole measure of journal quality lend weight to the need for complementary measures.