Answered By: Sarah Griffis Last Updated: Apr 20, 2017 Views: 10
Thomson Reuters’ Journal Citation Reports® provides a means for evaluating leading journals with statistical information based on citation data. By gathering articles' cited references, JCR helps measure research influence and impact in both the journal and category levels, and illustrates the relationship between citing and cited journals.
The JCR covers more than 9,100 journals from over 2,200 publishers in approximately 230 disciplines from 78 countries. There are two editions: The Sciences Edition, covering over 6,500 journals; the Social Sciences Edition, coving over 1,900. The Sawyer Library provides access to only the Social Sciences Edition.
An Impact Factor (IF) provides a quantitative assessment of a journal's influence or impact. According to Thomson Reuters, the Journal Impact Factor is the frequency with which the “average article” in a journal has been cited in a particular year. A journal’s Impact Factor is determined by dividing the number of citations in the JCR year by the total number of articles published in the two previous years.
[The formula is n=number in the subject category
n-rank/n-1 x 100 =percentile]
A Journal Impact Factor of 4.0 means that, on average, the articles published in that journal within the past three years have been cited four times. There must be at least two years of data in order to calculate the Impact Factor.
Using Impact Factors (IF) Wisely:
As Thomson Reuters indicates on their Information About page, a researcher should not depend entirely on JCR data to evaluate a journal because:
· IF only includes journals indexed by Thomson Reuters Scientific (ISI).
· IF does not evaluate individual researchers.
· Journals can only be compared within the same discipline. Citation results vary widely across disciplines.
· The number of articles found in journals include both research and review articles. "Citation counts in JCR do not distinguish between citations to letters, reviews, or original research articles, even though only original research and review articles are used in IF calculations."
· Title changes or changes in format of a journal affects the IF.
For further instruction in the use of JCR and the Impact Factor, see the JCR and Impact Factor LibGuide.