Measure of the frequency with which the “average article” in a journal has been cited in a particular year, used to measure the importance or rank of a journal.
The impact factor (IF) can help evaluate a journal’s relative importance, especially when compared with other journals in the same field. The IF is calculated by dividing the number of citations of articles published in the journal during the most recent 2 years by the total number of articles published in the same time period.
The equation is as follows:
2019 Journal Impact Factor = A/B
A = the number of times articles published in 2017 and 2018 were cited by indexed journals in 2019 B = the total number of citable items published in 2017 and 2018.
In this definition “citable items” are articles, reviews and proceedings papers, while items like editorials, corrections, notes, retractions and discussions are not included.
The Journal Impact Factor is published as part of the Journal Citation Report (1) based on the Web of Science source data. The 2019 report included 11,877 journals from 81 countries. In 2019 the publication with the highest IF was CA: A Cancer Journal for Clinicians with an IF of 223, followed by Nature Reviews Materials with an IF of 74 and The New England Journal of Medicine rounding out the top three with an IF of 71. The top 1500 journals all had IFs above 6.8 (2)
What does the IF tell about a researcher?
Journals with higher impact factors are generally considered more important and prestigious than those with lower ones and therefore publishing in these journals increases a researcher’s reputation and professional standing. For expert identification and prioritization the IF can be one of several factors taken into consideration when looking at a researcher’s publication history.
In Monocl Professional the Journal Impact Factor is listed in parentheses after the journal title abbreviation.