Assessing the academic quality of a particular journal or article is important. It can:
The JCR "impact factor" historically has been the main factor used to judge the relative importance of a journal in its field. However, because the index is based on only publications indexed in Web of Science the validity of this measurement is being disputed particularly in non-scientific fields and we are now seeing the other "impact" factors being published.
The JCR Journal Impact Factor is the average number of times articles from a journal published in the past two years, indexed in the Web of Science, have been cited in the JCR year. For example:
(from the Thomas Reuters site http://admin-apps.webofknowledge.com/JCR/help/h_impfact.htm)
How do I find a journal's "impact" factor?
Search for the published "impact" factor(s).
Are there other ways to evaluate "impact?"
Since one of the main criteria for calculating "impact" is the number of times articles from a journal are cited.
For more informaion: http://www.harzing.com/pop.htm