Measuring Research Impact: Journal Metrics

• Journal Impact Factor: Frequency with which the 'average article' in a journal has been cited over a particular year.
• The calculation is based on a recent two-year period of citations and involves dividing the number of times the journal's articles were cited by the number of articles that published in the journal in the two years. In addition to the standard 2-year metric, a 5-year impact factor is also available.
• Updated annually 
• Available in Journal Citation Reports (JCR) by Clarivate Analytics. You can look up individual journals or browse by category (i.e. discipline).
• Limited to journals indexed in Web of Science (Web of Science Selection process). Journals not indexed in this database do not have an impact factor.
• Science and social science are more likely to have impact factors than humanities journals. . 

Learn more about Journal Citation Reports: http://clarivate.libguides.com/jcr  / Video intro

• Eigenfactor = Measurement of the 'importance' or 'influence' of a journal. Citations from prominent journals are weighted more than citations from lesser known journals.
• Article Influence: Calculated by dividing the Eigenfactor by the number of articles published in the journal.
• Both scores use a 5-year citation window and use data from Journal Citation Reports.
• Available on Eigenfactor website, or via Journal Citation Reports.
• The sum of the Eigenfactor scores of all journals listed in Journal Citation Reports (JCR) is 100. If a journal has an Eigenfactor score of 1.0, it has 1% of the total influence of all indexed publications.

• Elsevier/Scopus alternative to Impact Factor, Uses data from Scopus, with a 3-year citation window.  (Scopus inclusion criteria)
• CiteScore calculates the average number of citations received in a calendar year by all items published in that journal in the preceding three years. See CiteScore FAQs to learn more.
• Available via Scopus.
• Not as established as Journal Impact Factor
• Some controversy: 
  • Is CiteScore, the new Elsevier-Scopus alternative to Impact Factor, favorable to Elsevier journals?
  • “Should CiteScore ever reach the level of prominence that Impact Factor currently holds, journals will face strong incentives to reduce or eliminate the news and editorials [front matter] that appeal many readers” (Enago Academy)

• A citation metric weighted by the prestige of a journal. Subject field, quality, and reputation of the journal have a direct effect on the value of a citation.  See detailed description of SJR.
• Based on Scopus data, with a 3-year citation window.
• Attempts to normalize for differences in citation behavior between subject fields. 
• Available on SCImago Journal and Country Rank website, which provides the SJR, journal H-index and other metrics, or via Scopus.
• SCImago Journal and Country Rank website provides journal rankings. Rankings are available for some disciplines that Journal Citation Reports does not cover, such as Art & Humanities. The ranking method is based on the Google PageRank algorithm.

• SNIP uses data from Scopus, with a 3-year citation window.
• Weights citations based on the total number of citations in a given field (subject), in an attempt to facilitate "more accurate between-field comparisons of citation impact."
• Available on CWTS Journal Indicators website, or via Scopus (on Sources page and on journal title's home page).

1. Journal impact metrics do not assess the quality of individual articles, their importance, or usefulness! The quality and impact of the author's work may extend beyond the impact of a particular journal.

2. "To say that because a researcher is publishing in a certain journal, he or she is more influential or deserves more credit is not necessarily true. There are many other variables to consider." (Jim Testa, a researcher for ThomsonReuters Scientific in a 2008 interview)

3. Journal Impact Factor, Eigenfactor, and CiteScore cannot be used to compare journals from different subject fields.

4. Citation-based journal impact metrics are higher in disciplines in which rapid citation is the standard. Fields with a more durable literature, such as mathematics, have a much smaller fraction of short-term citations and hence lower journal impact factors.

5. Journal impact metrics can be manipulated (The Journal that could not stop citing itself ; Coercive Citation in Academic Publishing)

The Journal Impact Factor (JIF): Science Publishing’s Miscalculating Metric. (2017)

Researchers and Scientific Groups Make New Push Against Impact Factors (2013)

Why we are not ready for radical changes in science publishing (2014)