What is Journal Impact Factor ?

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An offshoot of citation analysis is Journal Impact Factor (JIF) which 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.

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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 is the Journal Impact Factor Calculated?

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Thomson defines impact factor as, “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 JCR year. The Impact Factor is calculated by dividing the number of citations in the JCR year by the total number of articles published in the two previous years. An Impact Factor of 1.0 means that, on average, the articles published one or two year ago has been cited one time. An Impact Factor of 2.5 means that, on average, the articles published one or two year ago has been cited two and a half times. Citing articles may be from the same journal; most citing articles are from different journals.”

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A journal's impact factor for 2008 would be calculated by taking the number of citations in 2008 to articles that were published in 2007 and 2006 and dividing that number by the total number of articles published in that same journal in 2007 and 2006. Below is how Thomson calculated the 2008 impact factor for the journal.