Journal Impact Factor (IF) is the frequency by which the average article published within a specific journal title is cited in a particular period. Expressed as a number, it represents a quantitative indication of the quality of a journal within the context of a subject category and may be used as the basis on which to make a judgment about choosing and selecting journals for the submission of manuscripts for publication. “Impact Factor” is the exclusive property of Thomson Reuters and is applied to journals listed in the annual Journal Citation Reports (JCR) and indexed in the Web of Science Core Collection. These databases are available through the University Library’s A-Z list of subject resources.
The most recent annual JCR datasets for Science and Social Sciences are for 2014. The impact factor for journals listed for 2014 was calculated by dividing the number of citations of a specific journal’s content in 2014 by the number of citable articles published in the previous 2 years, 2012 and 2013, i.e.
n = total citations to articles published in the journal 2014
x = 2014 citations to articles published 2012-2013 (subset of n)
y = number of citable articles published 2012-2013
z = x/y = Impact Factor (IF)
The Impact Factor (IF) is the ratio between citations and recently published citable items, so higher IFs indicate a greater likelihood of an article published in that journal reaching a research audience within its subject category. The calculation leads to variations in the annual JCR listings, new journals in a field take time to feature and differences among disciplines mean Impact Factor can’t be used as an absolute indicator of quality. However by using the IF to produce a ranked list you can usefully determine in which quartile a journal is listed for a given subject category and be confident that journals in Q1 and Q2 are the titles with the highest impact factors, an indicator of “research excellence” and a target for research outputs. There are caveats about the use of this type of measure (metric or indicator) for the assessment of the quality of research (Wilsdon et al. 2015) which we will cover in future blog posts in this category. Contact Colin MacLean, University Library: firstname.lastname@example.org, for more information on Journal Impact Factors.
WILSDON, J., et al., 2015. The metric tide: report of the independent review of the role of metrics in research assessment and management. [online]. London: HEFCE. Available from: http://www.hefce.ac.uk/pubs/rereports/Year/2015/metrictide/Title,104463,en.html