CiteScore
{{Short description|Metric of academic journal importance}}
{{Citation metrics}}
CiteScore (CS) of an academic journal is a measure reflecting the yearly average number of citations to recent articles published in that journal. It is produced by Elsevier, based on the citations recorded in the Scopus database. Absolute rankings and percentile ranks are also reported for each journal in a given subject area.{{cite web | title=How are CiteScore metrics used in Scopus? | website=Scopus: Access and use Support Center | date=2022-07-29 | url=https://service.elsevier.com/app/answers/detail/a_id/14880/supporthub/scopus/ | access-date=2023-05-24}}
This journal evaluation metric was launched in December 2016 as an alternative to the Journal Citation Reports (JCR) impact factor (IF), calculated by Clarivate. CiteScore is based on the citations collected for articles published in the preceding four years, instead of two or five in the JCR IF. This enhanced methodology was introduced with the release of CiteScore 2019 in June 2020. At launch, CiteScore's neutrality was questioned by bibliometrics experts like Carl Bergstrom, who found it appeared to favour Elsevier's titles over Nature's.{{cite web|first1=Carl|last1=Straumsheim|access-date=2023-08-13|title=How to Measure Impact|url=https://www.insidehighered.com/news/2016/12/14/exploring-citescore-elseviers-new-journal-impact-metrics|website=Inside Higher Ed}}
Calculation
In any given year, the CiteScore of a journal is the number of citations, received in that year and in previous three years, for documents published in the journal during the total period (four years), divided by the total number of published documents (articles, reviews, conference papers, book chapters, and data papers) in the journal during the same four-year period:
For example, Nature had a CiteScore 2021 of 70.2:{{Cite web |title=Source Details: Nature |url=https://www.scopus.com/sourceid/21206 |access-date=2023-02-05 |website=Scopus |publisher=Elsevier}}
For example, the 2017 CiteScores were reported first in 2018 when all data was available completely. CiteScores are typically released in late May,{{Cite press release |title=Elsevier releases 2017 CiteScore™ values |date=May 31, 2018 |publisher=Elsevier |location=Amsterdam |url=https://www.elsevier.com/about/press-releases/science-and-technology/elsevier-releases-2017-citescore-values}} approximately one month earlier than the JCR impact factors.{{Cite web |last=Collier |first=Keith |date=June 30, 2021 |title=The 2021 Journal Citation Reports: A continuing evolution in journal intelligence |url=https://clarivate.com/blog/the-2021-journal-citation-reports-a-continuing-evolution-in-journal-intelligence/ |website=Clarivate}} Scopus also provides the projected CiteScores for the next year, which are updated every month.
= Pre-2020 formula =
Before 2020, the score was calculated differently: in a given year, the CiteScore of a journal was the number of citations received in that year of articles published in that journal during the three preceding years, divided by the total number of "citable items" published in that journal during the three preceding years:{{Cite web |title=Journal Metrics - FAQs |url=https://journalmetrics.scopus.com/index.php/Faqs |url-status=dead |archive-url=https://web.archive.org/web/20200414230825/https://journalmetrics.scopus.com/index.php/Faqs |archive-date=2020-04-14 |access-date=2023-02-05 |website=Scopus |publisher=Elsevier}}
For example, Nature had a CiteScore of 14.456 in 2017:
Because the calculation method changed, knowing the calculation date is an important detail when comparing CiteScores. For example, the Nature CiteScore for 2017 calculated with the post-2020 method is 53.7.
Comparison to JCR Impact Factor
File:CS-IF2017.png (ACS, green) and Nature group journals (blue), 2017 data. The values for Nature journals lie well above the expected ca. 1:1 linear dependence because those journals contain a significant fraction of editorials.]]
CiteScore was designed to compete with the two-year JCR impact factor, which is currently the most widely used journal metric.{{cite journal |last1=Gray |first1=Edward |last2=Hodkinson |first2=Sarah Z. |year=2008 |title=Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals. |url=https://journals.library.ualberta.ca/istl/index.php/istl/article/view/2451 |journal=Issues in Science and Technology Librarianship |issue=54 |doi=10.5062/F4FF3Q9G}}{{cite web |title=Journal Citation Reports: JCR ® |url=https://library.nd.edu.au/researchers/journalrankings/jcrs |url-status=dead |archive-url=https://web.archive.org/web/20210225045749/https://library.nd.edu.au/researchers/journalrankings/jcrs |archive-date=2021-02-25 |access-date=2023-02-05 |work=The University of Notre Dame Australia}} Their main differences are as follows:
| Class="wikitable"
!Parameter !!JCR IF!! CiteScore | ||
| Evaluation period (years) | 2 | 4 |
| Database | JCR | Scopus |
| No. indexed journals (Mar 2022) | 20,994 | 28,134 (Active Journals) |
| Access | Subscribers | Anyone |
| Evaluated items | Articles, reviews | Articles, Reviews, Conference Papers, Data Papers,
Book chapters |
Another difference is the definition of the "number of publications" or "citable items".{{Cite journal|last=Van Noorden|first=Richard|title=Controversial impact factor gets a heavyweight rival|journal=Nature|doi=10.1038/nature.2016.21131|pmid=27974784|volume=540|issue=7633|pages=325–326|year=2016|bibcode=2016Natur.540..325V|doi-access=free}}