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)
What is Journal Citation Reports?
Journal Citation Reports (JCR) offers a systematic, objective means to critically evaluate the world's leading journals, with quantifiable, statistical information based on citation data. By compiling articles' cited references, JCR helps to measure research influence and impact at the journal and category levels, and shows the relationship between citing and cited journals.
Journal Citation Reports helps in identifying the most frequently cited journals in the science and social science fields. JCR presents a systematic and objective way to assess leading journals and their impact within their subject categories and at the research level. Data can be sorted by clearly defined fields including: Impact Factor, Immediacy Index, Total Cites, Total Articles, Cited Half-Life, and Journal Title. Features include: Most frequently cited journals, highest impact journals, hottest journals, leading journals, and most published articles.