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A Correction Regarding Bibliographic Impact Factors

Hernán, Miguel A.

doi: 10.1097/EDE.0b013e3181b074a7
Editorial Post-Script

My recent editorial discussed the appropriateness of Thomson Reuters bibliographic impact factor (BIF) as a measure of a journal's scientific impact.1 As Porta did before,2 I warned that “a journal's BIF can be increased simply by publishing commentaries and other nonsubstantive articles that cross-cite themselves.” In fact, I calculated that Epidemiology's recent series of editorials, commentaries, and letters3–13 on the BIF had resulted in 28 “free” citations that will increase the numerator, but not the denominator, of Epidemiology's BIF.

Though my argument was generally valid, it turns out that my calculations were incorrect. As George Davey-Smith kindly reminded me (personal communication), citations to an article during the calendar year in which the article was published are not used in the calculation of the BIF. Thus the correct number of free citations resulting from Epidemiology's series on the BIF is not 28 but 31. This number includes 10 citations from the above paragraph. Publishing corrections may be embarrassing, but it increases a journal's BIF.

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© 2009 Lippincott Williams & Wilkins, Inc.