An Impact Factor is one measure of the relative importance of a journal or scientist to science and social science literature and research.
Each index or uses a different methodology and produces slightly different results, revealing the importance of using several sources to judge the true impact of a journal's or scientist’s work.
Careful use of these impact data is essential, and should be based on a thorough understanding of the methodology used to generate impact factors. There are controversial aspects of using impact factors:
|Measure of journal(s) impact||X||X|
|Includes theses & popular magazines||X|
|Considers quality of citing journal||X|
Adjusts for disciplinary patterns, permitting cross-discipline comparisons
|Measure of author impact||X|
|Uses 2 years of data||X|
|Uses 5 years of data||X|
|Uses all published years/articles||X|