5-Year Impact Factor

The 5-Year Impact Factor is a similar journal metric to Clarivate Analytics' Impact Factor which applies a 5-year window instead of a 2-year window (i.e. it is a measure of the average number of citations received in a particular year by articles published in the journal in the five preceding years). For example, the 5-Year Impact Factor for 2018 is calculated as follows:

• A = citations received in 2018 to articles published in the journal in 2013, 2014, 2015, 2016 and 2017
• B = the total number of "citable items" published in the journal in 2013, 2014, 2015, 2016 and 2017
• 5-Year Impact Factor 2018 = A/B

As for the Impact Factor, the 5-Year Impact Factor is calculated using data from the Web of Science database and it applies the same definition of "citable items" (i.e. Articles, Reviews and Proceedings Papers; not Editorials, Corrections, Notes, Retractions, Discussions and Letters to the Editor) as its 2-year counterpart.

Note that a base of five years may be more appropriate for journals in certain subject fields because the body of citations may not be large enough to make reasonable comparisons otherwise, or because it may take longer than two years to publish and distribute leading to a longer period before others can cite the work.

ISI Ranking

Journals are often ranked by Impact Factor within an appropriate Clarivate Analytics subject category. As there are now two types of Impact Factor published – a 2-year one and a 5-year one – this rank may differ. So care is needed when assessing these ranked lists to understand which of the two metrics is being used. In addition, journals can be categorized into multiple subject categories, giving them different ranks within each subject area. Consequently, a rank should always be seen in the context of a subject category.