Impact Factors

Definition

• Impact factors are calculated by Thomson Scientific, the producer of the Web of Science citation index.
  
• The impact factor of Journal A = number of citations to articles in Journal A in Web of Science in previous two years, divided by number of original research articles and reviews published by Journal A in the previous two years.

Where To Find Impact Factors and Journal Rankings

• Thompson Scientific publishes current impact factors in the Journal Citation Reports( JCR ).
  
• JCR includes impact factors for individual journal titles and lists of highly ranked journals by subject.
  
• The JCR print volumes are available at the Reference Desk in Ellis Library along with some detailed supplementary material on microfiche.

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  • Journal Citation Reports Science Edition
    Ellis Library Ready Reference Z7403 .S32
  • Journal Citation Reports Social Science Edition
    Ellis Library Ready Reference Z7163 .S62
    
• JCR volumes covering journal rankings for the previous year are usually published in late summer
  
• There is not a humanities edition of the JCR.
  
• Not all science and social science journals are included in the Journal Citation Reports

• The Science Gateway provides a free online listing of impact factors for selected science journals as well as some other ranked lists for both social science and science journals.
  
• Additional journal ranking methods

Further Information on Impact Factors

• The Agony and the Ecstasy: The History and Meaning of the Journal Impact Factor (2005 paper by the chairman of the producing company Thomson Scientific)
  
• The Number That's Devouring Science (Chronicle of Higher Education, 2005)