Journal Impact Factor (JIF)
The Journal Impact Factor (JIF) uses citation data to
assess and track the impact of a journal in relation to other journals,
the impact factor is recalculated each year and is based on the mean
during that year of the papers published in that journal during the
previous 2 years.
Journal Impact Factors are listed within Journal Citation Reports (JCR), accessible via InCites\Web of Science. JCR covers science and technology, and the social sciences and is updated annually in two editions. The Science edition covers over 8,000 journals and the Social Sciences edition covers over 2,600 journals.
For the 2017 edition (and onwards), the JCR includes details of the citation distribution of articles, helping to show whether the JIF is driven by a large number of well-cited papers, or by a small number of highly-cited outliers.
JCR offers additional indicators of a journal's impact, including the Eigenfactor and Article Influence scores, although these are less commonly used.