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September 9, 2009

The Journal Impact Factor Denominator: Defining Citable (Counted) Items

Author Affiliations

Author Affiliations: Bibliographic Policy, Journal Citation Reports, Thomson Reuters, Philadelphia, Pennsylvania.

JAMA. 2009;302(10):1107-1109. doi:10.1001/jama.2009.1301

Over its 30-year history, the journal impact factor has been the subject of much discussion and debate.1 From its first release in 1975, bibliometricians and library scientists discussed its value and its vagaries. In the last decade, discussion has shifted to the way in which impact factor data are used. In an environment eager for objective measures of productivity, relevance, and research value, the impact factor has been applied broadly and indiscriminately.2,3 The impact factor has gone from being a measure of a journal's citation influence in the broader literature to a surrogate that assesses the scholarly value of work published in that journal. These misappropriated metrics have been used to assess individual researchers, institutions, and departments.