Impact Factor

What is Impact Factor? Why use IF?

The impact factor (IF) is a measure of the frequency with which the average article in a journal has been cited in a particular year. It is used to measure the importance or rank of a journal by calculating the times it's articles are cited.
An offshoot of citation analysis is Journal Impact Factor (JIF) that is used to sort or rank journals by their relative importance. The underlying assumption behind Impact Factors (IF) is that journals with high IF publish articles that are cited more often than journals with lower IF. Impact factors may be used by:

  Authors to decide where to submit an article for publication
  Libraries to make collection development decisions
  Academic departments to assess academic productivity
  Academic departments to make decisions on promotion and tenure

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. Calculation of 2010 IF of a journal: A = the number of times articles published in 2008 and 2009 were cited by indexed journals during 2010. B = the total number of "citable items" published in 2008 and 2009. A/B = 2010 impact factor.
An Impact Factor of 1.0 means that, on average, the articles published one or two year ago have been cited one time. An Impact Factor of 2.5 means that, on average, the articles published one or two year ago have been cited two and a half times. Citing articles may be from the same journal; most citing articles are from different journals. The Impact Factor (IF) graph reflects only the citations retrieved from the Open Science Index.