Answered By: Michael Mackin Last Updated: Oct 07, 2016 Views: 5
An academic journal's impact factor is the average number of times articles from that journal published in the past two years have been cited in Journal Citation Reports (InCites). Impact factor is an attempt to measure the journal's relative importance in its field, so the higher the impact factor, the more important the journal.
Issues of Validity and Reliability
There are many factors, however, that affect the impact factor calculation. When determining the validity or reliability of an impact factor, it is important to take into consideration factors such as journal size, date of publication, presence of review articles, journal title changes, research versus clinical journals, and changing fields, because these can artificially increase or decrease the impact factor.
Finding the Impact Factor
You can easily find the impact factor of a journal by searching for the journal title in Journal Citation Reports (InCites), which provides rankings and comparison tools, as well as in Scopus. You may also calculate the impact factor by dividing the number of times that all items published in a journal in the previous two years were cited during the current year by the total number of "citable items" published by that journal in the previous two years.
For example, according to Journal Citation Reports (InCites), Lancet had an impact factor of 45.217 in 2014. This was calculated as follows:
This means that, on average, articles published in Lancet in 2012 and 2013 have been cited around 45.217 times.
Journal Impact Factors. (n.d.). Retrieved March 01, 2016, from http://libguides.lib.msu.edu/c.php?g=95500
Kear, R., & Colbert-Lewis, D. (2011). Citation Searching and Bibliometric Measures. College and Research Libraries News, 72(8), 470-474. Retrieved March 1, 2016.
The Thomson Reuters Impact Factor. (n.d.). Retrieved March 01, 2016, from http://wokinfo.com/essays/impact-factor/