Definition: The journal impact factor measures the importance of a journal by calculating the times it's articles are cited.
How Impact Factor is Calculated: The calculation is based on a two-year period and involves dividing the number of times articles were cited by the number of articles that are citable.
Experts stress that there are limitations in using impact factors to evaluate a scholar's work. There are many reasons cited for not relying on impact factor alone to evaluate the output of a particular individual. Among these are the following:
According to Jim Testa, a researcher for ThomsonReuters Scientific, the most widespread misuse of the Impact Factor is to evaluate the work of an individual author (instead of a journal). "To say that because a researcher is publishing in a certain journal, he or she is more influential or deserves more credit is not necessarily true. There are many other variables to consider." (interview 6/26/2008 in Thomson Reuters blog entry)
For an overview on the topic, see the Introduction under the Journal Rankings tab.
To use Journal Citation Reports, follow the steps below:
For more information about Journal Citation Reports, click on the Information for New Users located in the upper right hand corner of the database opening page, or view the Journal Citation Reports tutorial created by Thomson ISI.
This tutorial demonstrates how to find journal impact factors in Web of Knowledge. However, the information on how to access Journal Citation Reports is for another library, and does not apply to the University of Michigan. Instead, to access JCR you should go to the University Library's homepage. Type journal citation reports into the search box and click go. Journal Citation Reports is the first thing listed under Databases.
Much of the content of this guide is based on a guide created at University of Michigan Library and which can be viewed here. Thank you to the group that created that guide and allowed us to make use of the content for our own guide.