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)
Journal Impact Factors
Journal Impact Factor is from Journal Citation Report (JCR), a product of Thomson ISI (Institute for Scientific Information). JCR provides quantitative tools for evaluating journals. The impact factor is one of these; it is a measure of the frequency with which the "average article" in a journal has been cited in a given period of time.
Journal Citation Reports® tutorial
Overview — Journal Citation Reports provides easy access to data that helps you evaluate and compare scholarly journals. It is an essential, comprehensive, and unique resource tool for journal evaluation, using citation data drawn from over 7,500 journals from over 3,300 publishers in over 60 nations.
Journal Citation Reports is the only source of citation data on journals. It includes virtually all specialties in the areas of science, technology, and the social sciences. Moreover, it shows the relationship between citing and cited journals in a clear, easy-to-use framework.
Journal Citation Reports can show:
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.