The Impact Factor is based on an algorithm used by Web of Science to determine how important a given journal is in its field.
How is Impact Factor (IF) calculated?
The journal Impact Factor is the average number of times articles from the journal published in the past two years have been cited in the Journal Citation Reports (JCR) year:
|A = the number of times that articles published in that journal in 2010 and 2011, were cited by articles in indexed journals during 2012.|
|B = the total number of "citable items" published by that journal in 2010 and 2011. ("Citable items" are usually articles, reviews, proceedings, or notes; not editorials or letters to the editor.)|
|2012 impact factor = A/B|
Be aware that 2012 impact factors are actually published in 2013; they cannot be calculated until all of the 2012 publications have been processed by the indexing agency.
Garfield E. The History and Meaning of the Journal Impact Factor. JAMA.2006; 295(1):90-93. doi:10.1001/jama.295.1.90.
Is this joking video an entirely accurate portrayal of impact factors? No. It is, however, representative of the frustration that academic publishing often entails. Choosing (or having to) publish a paper in a journal with a low impact factor is not always indicative of the quality of either, but it may feel that way - and be treated that way.
|The idea of the impact factor was first introduced by Eugene Garfield in 1955. He is an American scientist, one of the founders of bibliometrics and scientometrics.|
His book Citation indexing - its theory and application in science, technology, and humanities (1979) is available through the University System of Maryland Libraries.
Many aspects of Impact Factor recommend it as a measure: it's convenient, can purport to be objective (numbers are numbers) and is widely accepted as valid. However, the measure has its detractors. Some of the points of protest are listed below.
Source: Duncan, L. ISI and Impact Factors. [Accessed June, 2014]