Differences in Impact Factor Across Fields and Over Time

Benjamin M. Althouse, University of Washington
Jevin D. West, University of Washington
Ted C. Bergstrom, University of California, Santa Barbara
Carl T. Bergstrom, University of Washington

Abstract

The impact factor of an academic journal for any year is the number of times the average article published in that journal in the previous two years are cited in that year. From 1994-2005, the average impact factor of journals listed by the ISI has been increasing by an average of 2.6 percent per year. This paper documents this growth and explores its causes.