Impact Factors

An Impact Factor is a quantitative measure of the relative importance of a journal, individual article or scientist to science and social science literature and research.

Each index or database used to create an impact factor uses a different methodology and produces slightly different results.  This is why it is important to use several sources to gauge the true impact of a journal's or scientist’s work.

This guide includes information on Journal Impact Factor, Author Impact Factor, Article Impact Factor, and Documenting Your Research Impact.

Informed and careful use of these impact data is essential, and should be based on a thorough understanding of the methodology used to generate impact factors. There are controversial aspects of using impact factors:

• It is not clear whether the number of times a paper is cited measures its actual quality.
• Some databases that calculate impact factors fail to incorporate publications including textbooks, handbooks and reference books.
• Certain disciplines have low numbers of journals and usage. Therefore, one should only compare journals or researchers within the same discipline.
• Review articles normally are cited more often and therefore can skew results.
• Self-citing may also skew results.
• Some resources used to calculate impact factors have inadequate international coverage.
• Editorial policies can artificially inflate an impact factor.

Curious about critiques of journal impact factors? Read on!

• Bornmann, Lutz, and Werner Marx. 2016. “The Journal Impact Factor and Alternative Metrics.” EMBO Reports 17 (8): 1094. https://doi.org/10.152/embr.201642823.
• Scully, C, and H Lodge. 2005. “Impact Factors and Their Significance; Overrated or Misused?” British Dental Journal 198 (April): 391.

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