The Journal Impact Factor was introduced by Eugene Garfield in the 1950s-1960s as a librarian's tool to compare journals for collection-development decisions. The two-year JIF is computed by dividing the count of citations received in year Y to items published in years Y-1 and Y-2 by the number of citable items in those years. The metric is mathematically inappropriate as a measure of the quality of individual articles or researchers because citation distributions within a journal are highly skewed: a small number of papers typically attract most citations. DORA and the Leiden Manifesto cite JIF misuse as the paradigmatic example of irresponsible metric use.
References
- Clarivate Journal Citation Reports. Larivière V et al. 'A simple proposal for the publication of journal citation distributions', bioRxiv, 2016. DORA recommendations.