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Bibliometrics: Citation Analysis and Research Impact: Citation Impact - Journal Level

Citation Impact - Journal Level Metrics - Journal Impact Factor & Cite Score

The simplest journal-level metric is the journal impact factor (JIF), the average number of citations that articles published by a journal in the previous two years have received in the current year, as calculated by Clarivate. Other companies report similar metrics, such as the CiteScore (CS), based on Scopus.

However, very high JIF or CS are often based on a small number of very highly cited papers. For instance, most papers in Nature (impact factor 38.1, 2016) were only cited 10 or 20 times during the reference year (see figure). Journals with a lower impact (e.g. PLOS ONE, impact factor 3.1) publish many papers that are cited 0 to 5 times but few highly cited articles.[15]

Journal-level metrics are often misinterpreted as a measure for journal quality or article quality. However, the use of non-article-level metrics to determine the impact of a single article is statistically invalid. Moreover, studies of methodological quality and reliability have found that "reliability of published research works in several fields may be decreasing with increasing journal rank",[16] contrary to widespread expectations.[17]

Citation distribution is skewed for journals because a very small number of articles is driving the vast majority of citations; therefore, some journals have stopped publicizing their impact factor, e.g. the journals of the American Society for Microbiology.[18] Citation counts follow mostly a lognormal distribution, except for the long tail, which is better fit by a power law.[19]

Other journal-level metrics include the Eigenfactor, and the SCImago Journal Rank.

 Source: Wikipedia, the free encyclopedia

Journal Impact Factors (Web of Science )


A journal's Impact Factor is a measure of the frequency with which the "average article" in a journal has been cited in a given period of time. 

The JIF is simple and easy to calculate – all you need to know is the number of scholarly works that a journal published in the last two years (also referred to as citable items) and how many citations they received from papers published in the JCR data year. Various factors influence how many citations could be accumulated including the typical number of references made in a paper, the age of papers referenced, the total number of papers published and even the meaning of a citation itself. Due to these differences, comparisons for the JIF should be made in category or between adjacent fields.

(Source: Clarivate. 2021. Introducing the Journal Citation Indicator webinar)

Suggestions for finding Impact Factors of particular journals:

  •  Look at the webpage of journal publishers, e.g. Elsevier - Tetrahedron Letters, as Impact Factors are sometimes indicated on the journals’ homepages.

Journal Citation Reports

Every journal has a story to tell.

Each year, millions of scholarly works are published containing tens of millions of citations.  Each citation is a meaningful connection created by the research community in the process of describing their research.  The journals they use are the journals they value.  The Journal Citation Reports (JCR) aggregates citations to our selected core of journals, allowing this vast network of scholarship to tell its story.

Source: Clarivate Analytics

What are Journal Citation Reports (JCR)?

To access Incites 2 (Clarivate Analytics) click here

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The Journal Citation Indicator (Web of Science)

"The Journal Citation Indicator (JCI) is a new way to measure the citation impact of a journal’s recent publications using a field-normalized calculation. This new approach provides a single value that is easy to interpret and compare, complementing current journal metrics and further supporting responsible use. Starting from the 2021 JCR release, it will be calculated for all journals in the Web of Science Core Collection".

In the last 20 years, the bibliometric community has devoted much attention to the issues of interpretation and comparison, devising more sophisticated ways to measure citation impact than by counting the number of citations. Among these, normalization has become the de facto standard – rather than using a citation count as a measure of impact, the citations received by a paper are compared against a cohort of similar papers and expressed as a ratio or percentile. The JCI is a normalized indicator which means that it accounts for variation and provides a number that can be more easily compared across disciplines.  The calculated value represents the average category-normalized citation impact for papers published in the prior three-year period.

The normalization steps make it more reasonable to compare journals across disciplines, but careful judgement is still required. Adjacent fields (e.g. those in the physical sciences) can be more readily compared since the bibliometric characteristics of scholarly publication are similar, and the value of a citation is more comparable. However, in the arts and humanities, citations provide a weaker signal of academic impact, and other qualitative measures should also be considered. Comparing journals in the arts and humanities to those in the sciences or social sciences based solely on their Journal Citation Indicator would be ill advised.

When compared to the Journal Impact Factor, most indicator values that are based on citations will be correlated – both the Journal Citation Indicator and the JIF are most affected by citations to citable items. However, differences between Journal Citation Indicator and JIF will occur for the following reasons:

• The time period of articles and reviews is slightly different, with the Journal Citation Indicator considering an additional year of content.

• The JIF calculation is based on citations made in the current year, whereas the Journal Citation Indicator sums citations across the whole time period following publication, up to the end of the current year.

• The JIF calculation includes unlinked citations – those that could only be attributed to a journal, but not linked to a specific item. Since CNCI is an article-level metric, unlinked citations are not counted in the Journal Citation Indicator.

• The JIF calculation counts all citations made to any item published in the journal (the numerator) and is not limited to only the citable items. The Journal Citation Indicator only counts citations made to the citable items – any citations to noncitable items (e.g. letters, news, editorials) are ignored.

(Source: Clarivate. 2021. Introducing the Journal Citation Indicator webinar)

Cite Score Metrics (Scopus)

Improved Citescore

The updated CiteScore 2022 metrics are now available on Scopus.

CiteScore metrics are calculated annually using the extensive Scopus dataset. Scopus offers these transparent and freely available metrics to support the research community, providing a more accurate and fair assessment of a journal's impact

We have updated the CiteScore methodology to ensure a more robust, stable and comprehensive metric which provides an indication of research impact, earlier. The updated methodology will be applied to the calculation of CiteScore, as well as retroactively for all previous CiteScore years (ie. 2018, 2017, 2016…). The previous CiteScore values have been removed and are no longer available.

Use CiteScore metrics to:

  • Find the best suited titles to submit your next paper
  • Create Reading lists for serial titles most relevant to your discipline
  • Evaluate a journal's reach, influence and impact
  • Avoid predatory journals

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