Measuring Research Impact

Although generally focused on number of citations articles within a publication receive, more recently, other measures have emerged as useful.  This section will provide an overview of major players in both citation and non-citation based metrics.  Each has its strengths and weaknesses and should be used in combination with other factors when evaluating a journal.

Journal Citation Reports provides a suite of citation-based metrics including:

Journal Impact Factor (JIF)

• How to:  Quick Guide: JIF
• What is it?:  Measures ratio between citations and recent citable items published in a journal
• Useful for:  Comparing the relative influence of journals within a discipline, as measured by citations
• Limitations :  Scope of journals included may be overly restrictive depending on discipline and some article types, such as reviews, are disproportionately represented

Journal Citation Indicator (JCI)

• How to: Quick Guide: JCI
• What is it?: Uses the mean Category Normalized Citation Impact (CNCI) from the three prior years to measure relative citation impact as the ratio of citations compared to a global baseline
• Useful for:  Comparing journals not necessarily in the same field (although most appropriate for assessing adjacent fields) since it controls for different disciplines, document types, and publication year
• Limitations:  Scores for a single journal influenced by number of subject categories the journal is in. 

Citation Distribution

• How to: Brief Video: Citation Distribution
• What is it?: Shows the frequency with which items published in the year or two years prior were cited
• Useful for: Determining if a small number of articles is driving the majority of citations
• Limitations : Debate as to whether this visual provides enough information without deeper analysis.

Scopus provides a suite of citation-based metrics including:

CiteScore

• How to: CiteScore Journal Metric - FAQs
• What is it?:  Average number of citations per peer-reviewed document (i.e., articles, reviews, conference papers, data papers and book chapters), using four years of data.
• Useful for: Simple comparison of the citation impact of peer-reviewed research within the same field.
• Limitations:  Cannot be used to compare journals from different disciplines.

SNIP (Source Normalized Impact per Paper)

• How to:  Scopus Tips & Tricks: SNIP
• What is it?:  Measures contextual citation impact by weighting citations based on the total number of citations in a subject field. The impact of a single citation is given higher value in subject areas where citations are less likely, and vice versa. 
• Useful for: Comparing journals from different subject fields.
• Limitations:  Does not correct for self citations.

SJR (SCImago Journal Rank)

• How to:  Scopus Tips & Tricks: SJR
• What is it?: Measures the weighted citations of journal articles, book series, and conference proceedings in journal publications during the three previous years.
• Useful for:  Normalizing for the subject field and appraising quality and reputation of the journal in its metrics.
• Limitations:  Difficult to replicate calculations and may not represent interdisciplinary work well.

Google Scholar provides somewhat simpler in design journal-level metrics including:

H5-Index

• How to:  Google Scholar Metrics Overview
• What is it?:  The largest number h such that at least h articles in that publication were cited at least h times each during a five-year period.
• Useful for: Quickly gauging the visibility and influence of literature beyond the reach of Web of Science and/or Scopus.
• Limitations:  Cannot be used to compare journals from different disciplines and journal/citation quality not reviewed.