Measuring the Measurable: A Commentary on Impact Factor


  • (The impact factor for year x, reported in June of year x + 1, is calculated as the total number of citations to articles published in the journal in years x – 1 and x – 2, divided by the number of “substantive articles” or “citable items” published in the journal in years x – 1 and x – 2. “Substantive articles” include “articles” and “reviews” and “proceedings papers”[2]; editorials/commentaries, correspondence, essays, and several other types of papers are not included in the denominator. Academic Emergency Medicine (AEM)'s 2011 impact factor, reported in June 2012, is calculated as follows: (486 citations in 2009 + 305 citations in 2010)/(194 articles in 2009 + 231 articles in 2010) = 791/425 = 1.861.).

  • A related article appears on page 1248.

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