Impact Factor

Impact Factor

Definition: The Journal Impact Factor is published each year by Thomson Reuters. It is a measure of the number of times an average paper in a particular journal is cited during the preceding two years.

For example:

A = the number of times articles published in a specific journal in 2009 and 2010 were cited by journals during 2011.

B = the total number of 'citable items' published by that journal in 2009 and 2010. ('Citable items' are usually articles, reviews, proceedings, etc.; not editorials or letters-to-the-editor.)

2011 impact factor = A/B.

Actual value is intentionally only displayed for the most recent year. Earlier values are available in the Journal Citation Reports from Thomson Reuters.

Journal Impact Factor
Cites in 2014 to items published in: 2015=801 Number of items published in: 2015=306
2013=958 2013=293
Sum: 1759 Sum: 599
Calculation: Cites to recent items       1759
Number of recent items  599   =2.937

5-Year Impact Factor


Note: A base of five years may be more appropriate for journals in certain fields because the body of citations may not be large enough to make reasonable comparisons, or it may take longer than two years to publish and distribute leading to a longer period before others cite the work.

5-Year Journal Impact Factor
Cites in{2014} to items published in: 2015=801 Number of items published in: 2015=306
2014=958 2014=293
2013=974 2013=297
2012=992 2012=281
2011=1006 2011=282
Sum: 4731 Sum: 1459
Calculation: Cites to recent items        4731
Number of recent items   1459   =3.243


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