CiteScore vs. Impact Factor

Journals are usually evaluated by means of citation metrics. Today two major journal-based metrics are in competition, i.e the Journal Impact Factor and CiteScore.

The Impact Factor has had a long reign in research and academics. Beginning in 1975 as a byproduct of the Science Citation Index, it provided a unique, objective means of rating journals based on their citations and quickly became a standard measure of journal quality.

It was in 2016 that Elsevier launched a new journal metric, CiteScore that takes direct aim at the hegemony of the Impact Factor, a product of Clarivate Analytics (formerly part of Thomson Reuters.) The two companies already have competing bibliographical citation databases in Scopus (Elsevier) and the Web of Science (Clarivate).

Impact Factor

Journal Impact Factor is a well-known citation metric that was created in the 1950s. The Journal Impact Factor is published through the Journal Citation Reports and is calculated from data compiled in the Web of Science database, thus covering approximately 11,000 journals with an indexed 2.2 million articles.

Impact Factor Limitations

• Since the Impact Factor is derived from journals indexed in the Web of Science, no other journals can have an Impact Factor.
• Since the Impact Factor only looks at citations in the current year to articles in the previous two years, it only works well for disciplines in which rapid citation is the standard.
• It doesn’t take into account disciplinary differences in expected numbers of citations.
• There is no JCR for arts & humanities, therefore no Impact Factor for those journals.

CiteScore

Elsevier launched a new citation metric in 2016 and is calculated with the 22,800 journals indexed in Scopus, which contains approximately 70 million articles.

CiteScore is another metric for measuring journal impact in Scopus. The calculation of CiteScore for the current year is based on the number of citations received by a journal in that year for the documents published in the journal in the past three years, divided by the documents indexed in Scopus published in those three years. This is how CiteScore of 2018 is calculated:​

Calculation of CiteScore in the Year 2018:

Now, CiteScore has arrived to compete with the Impact Factor, luring users in with these benefits:

• It is free to access on the Scopus Journal Metrics website (JCR is a paid subscription.)
• It is calculated from the Scopus journal list, which is much larger than the Web of Science list and includes more social sciences and humanities journals.
• It provides a 3-year citation window, rather than the 2-year window of the Impact Factor.

IF-CiteScore Similarities

Similar Principles: Both metrics are based on similar principles: the number of citations received by a journal in a given year to papers published in a given period of time, over the number of papers published by that journal in that time period.

Update Frequency: Both metrics are calculated and published yearly.

IF-CiteScore Differences

Period of Time for Calculation: Journal Impact Factor calculates the metric using the two previous years as a basis for the citation count, CiteScore uses a three-year period.

Areas such as Immunology or Genetics and Molecular Biology cite a substantially greater proportion of articles in the two-year window than papers in Arts and Humanities or Social Sciences.

Transparency in Calculation: Calculations in Journal Impact Factor are based on hidden data, they are opaque, and their quality used to calculate the Impact Factor was criticized.

Easy access to the complete list of cited and citing records used to calculate a given Impact Factor is not possible, even with full access to the Web of Science.

However, citing and cited documents are available through a one-link distance for a Scopus-subscribing institution or individual in CiteScore.

Number of Published Articles in Given Period of Time: Scientometricians have difficulties identifying the number of articles published by a journal in a year. Since the 1980s, Journal Impact Factor calculations have defined the denominator by using an algorithm based on a number of criteria to allocate “points” to the contribution, as a proxy for “the amount and type of information the article contains”.

In contrast, CiteScore includes all the documents published in a journal. There are more articles to cite but also fewer citations received, which reinforces the lack of transparency of the previously mentioned Journal Impact Factor.

Journal Coverage: The Web of Science covers 11,000 journals compared to almost 23,000 journals by Elsevier.

Despite the greater coverage of CiteScore, journal selection criteria are also not perfect. Apart from several quality-related criteria (e.g., journal policy, content, regularity), Scopus uses other criteria to re-evaluate journals. Among these criteria, citation rate or clicks on scopus.com (all of them if lower than 50% of the average in the field) would be reasons to be excluded from the Scopus catalog and subsequently from the CiteScore analysis.