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Impact Factor

What is "impact factor"?

Impact factor is a measure of the frequency with which the "average article" published in a given scholarly journal has been cited in a particular year or period and is often used to measure or describe the importance of a particular journal to its field. The Thomson-Reuters (formerly Institute for Scientific Information (ISI)) ranks, evaluates, and compares journals within subject categories and publishes the results in Journal Citation Reports .  The new rankings come out in the Spring, for the previous year's journals.  Three years worth of data are required to calculate a Journal Impact Factor.

The formula to determine the 2008 impact factor for a journal would be calculated as follows:

A = the number of times articles published in the journal during 2006-7 were cited by other journals during 2008
B = the number of articles or reviews that were published in the journal during 2006-7

2008 Impact factor for a journal = A/B

How to find a journal's impact factor or relative importance

From the library homepage, search " Journal Citation Reports" in the easy search box. 

shows easy search for journal citation

The grey box directly under your search results should read, "Your search Journal Citation Reports matched a  journal/magazine/database title(s)."

The next screen will list " Thomson."

sfx search for journal citation reports


Click on the link that says " THOMSON REUTERS DATABASES"

Select the Science or Social Science Edition, select a year, and choose to view a group of journals, search for a specific journal, or view all journals. You may view a group of journals by Subject Category (such as Agricultural Engineering, Astronomy, or Biology), by Publisher, or by Country/Territory.

Journal Citation Reports


Impact factors have a huge, but controversial, influence on the way published scientific research is perceived and evaluated. Numerous criticisms have been made of the system:

  1. Journal impact factors depend on the research field: high impact factors are likely in journals covering large areas of basic research and less likely in more subject-specific journals.
  2. Although Journal Citation Reports includes some non-English journals, the index is heavily skewed toward English-language journals, leaving out important international sources.
  3. Researchers may be more likely to pursue fashionable topics that have a higher likelihood of being published in a high-impact journal than to follow important avenues that may not be the as popular.

Alternative ways of ranking journals

  • Eigenfactor.org: Ranking and mapping scientific knowledge
    • The Eigenfactor algorithm ranks journals much as Google ranks websites .
  • The Australian Research Councilhas undertaken the project of developing journal rankings
    • 20,712 unique peer reviewed journals have been included in the ERA 2010 Journal List.

Learn more