Journal impact factor (JIF) was developed to help libraries decide which journals to purchase.  Over the ensuing decades, it became widely used as an indicator of prestige.  Authors often look at JIF to determine where to submit their research.  Tenure & promotion committees, grant agencies, or hiring committees may also note the impact of journals in which candidates have been published.  This use of JIF to assess researchers' merit is highly controversial.

A journal's impact factor is based on two numbers:

• Number of citations referencing substantive articles published in that journal over the past two years (numerator)
• Number of articles published in that journal over the past two years (denominator).

So, it can be expressed as: # citations / # articles.  If Journal X published 108 articles over the past two years and the articles were collectively cited 512 times, Journal X would have an impact factor of 4.741.

Recommendations for Using JIF

Do:

• Use JIF in addition to other available indicators of journal  quality and impact.  Journals can "game" their impact factor, and the way Thomson Scientific (a for-profit company) arrives at individual JIFs is not transparent (see PLoS Medicine article).

Don't:

• Place undue weight on small differences in impact factor.  A journal with an impact factor of 14.802 is not necessarily "better" than one with an IF of 14.798.
• Use JIF as the sole or primary measure of an individual researcher's impact.
• Rely on JIF to assess the quality of very new (<2 years) journals.

To find the impact factor of a journal, you'll need access to Thomson Scientific's Journal Citation Reports (JCR).  This is a subscription-based product.

1. Go to the OSU Libraries' A - Z Databases page.

2. Find the entry for Journal Citation Reports (InCites) and click on it. You can use the other JCR option, too; this one simply has enhanced features.

You'll notice that most of the top journals are broad scientific journals or biomedical journals.  What constitutes a "high" impact factor varies between disciplines.  Click "Select category" to narrow to a discipline.  If you're looking for the JIF of one particular journal, you can use the search box to locate it.