Citation Analysis and Metrics: Citation-based Metrics
Citation-based Metrics
Research impact is often measured using quantitative methods such as citation counts, the h-index, and journal impact factors. It can also be described qualitatively. Currently, there is no one tool or system that completely measures impact. Each database or tool uses its own measurement systems, indices, data and authority files. And it is difficult to use these tools to compare across disciplines that have different research and publication practices. There is no one number to perfectly or “correctly” represent the research impact of an individual or a group of researchers.
Below are some of the more common metrics and tools you can use to measure author and journal impact.
Author Impact
An author's impact on their field or discipline has traditionally been measured using the number of times they have published and the number of times their academic publications are cited by other researchers. Although the simplest way to demonstrate your impact is to create a list of your publications and the number of times they have been cited, numerous algorithms based on publication data have also been created. Below are some of the more common metrics and tools you can use to measure research impact.
h-index
- The number of publications (h) that have received (h) or more citations. For example, an author with an h-index of 5 has 5 papers cited at least 5 times.
- An author's h-index can be found in many citation databases, including Web of Science and Scopus (Fondren access via databases page)
- NOTE: An author's h-index may differ in different databases. This is because databases index different journals and cover different years. For example, Scopus only considers works from 1996 or later, while the Web of Science calculates the h-index using all years that an institution has subscribed (as a result, the Web of Science h-index might look different when searched across institutions)
i10-index
- Used only in Google Scholar, counts the number of publications with at least 10 citations.
- Available in the My Citation feature
- Limited to works indexed by Google Scholar
Journal Impact
Journal impact metrics attempt to quantify the importance of a particular journal in a field. They take into account the number of articles published per year and the number of citations to articles published in a particular journal. These metrics are one factor to consider when deciding on where to publish. Like author impact measurements, journal impact metrics have limitations and no single measure gives a complete assessment. Below are some of the more common metrics and tools you can use to measure journal impact (adapted from UNC Libraries' "Measure Your Research Impact: Journal Impact").
Impact Factor
- Measures frequency with which the "average" article in a journal has been cited in a particular year or other defined time period
- Calculated A/B
- A=Number of citations in the current year to items published in the journal in the previous two years
- B=Total number of articles published in the journal in the previous two years
- CANNOT be used to compare journals from different disciplines
- Can be found in Journal Citation Reports (Fondren access via databases page)
- Only includes journals indexed by Web of Science
Eigenfactor
- Measures the overall "value" provided by all articles published in a journal in one year.
- Citations from well-known, perceived higher-quality journals are weighted more than citations from lesser-known journals
- Can be used to compare journals from different disciplines
- Can be found in Journal Citation Reports (Fondren access via databases page) or at eigenfactor.org
ScImago Journal Ranking (SJR)
- Designed to measure "prestige." Accounts for number of citations received by a journal and importance of the journals that citations came from.
- Citations from more prestigious journals (higher SJR) weighted more than citations from less prestigious journals (lower SJR)
- Can be used to compare journals from different disciplines
- Found in Scopus (Fondren access via databases page)
Source Normalized Impact per Paper (SNIP)
- Measures actual citations received relative to citations expected for the journal’s subject field
- Can be used to compare journals from different disciplines
- Found in Scopus (Fondren access via databases page)
CiteScore
- Measures average citations received per document published in the journal
- Score based on the number of citations to documents (articles, reviews, conference papers, book chapters, and data papers) by a journal over four years, divided by the number of the same document types indexed in Scopus and published in those same four years.
- Found in Scopus (Fondren access via databases page)