Journal Citation Reports is sourced from Web of Science Core Collection, Journals must undergo a rigorous evaluation by our editorial team in order to be covered in Web of Science Core Collection. This article-level citation data is aggregated to the journal-level at the end of the year to create the indicators available in JCR. Over 11,500 titles from the Science Citation Index-Expanded and Social Sciences Citation Index are covered in JCR. The Science and Social Science editions of JCR are released annually.
This guide outlines:
The Journal Impact Factor identifies the frequency with which an average article from a journal is cited in a particular year. You can use this number to evaluate or compare a journal’s relative importance to others in the same field or see how frequently articles are cited to determine which journals may be better for your collection.
Example of 2017 Impact Factor calculation
The numerator looks at citations in a particular JCR year to a journal's previous two years of content. For example, the 2017 Journal Impact Factor for a journal would take into account 2017 items that cited that journal's 2015 or 2016 content. The numerator includes citations to anything published by the journal in that 2015-2016 timeframe.
The denominator takes into account the number of citable items published in the journal in 2015 and 2016. Citable items include articles and reviews. Document types that aren't typically cited, e.g.letters or editorial materials, are not included in the Impact Factor denominator.
The calculation is based on citations, hence publications in journals with higher IF may have higher chance of being cited as compared to publications published in journals with relatively lower IF.
1 - Search by Journal Title
2 - Search by Subject Category
Apart from Journal Impact Factor, Journal Citation Reports provide other metrics such as 5-year Impact Factor, Eigenfactor Scores, Article Influence Score and Immediacy Index. Refer to other parts of the guide to know more about these metrics.
You could click “Customize Indicators” to define the metrics you wish to compare the journals with.
The 5-year Impact Factor is the average number of times articles from a journal published in the last five years have been cited in the JCR year (as compared to the last 2 years for IF).
► The advantage of 5-year Impact Factor
The calculation of the 5-year Impact Factor includes a longer time span which allows more citation activities. It may be more appropriate for subject disciplines such as Arts and Humanities which take a longer time to have the citation activities.
Eigenfactor is freely available.Data is supplied for this metric by Thomson Reuters (ISI) which provides Eigenfactor for journals and article influence for each article in a journal.
Article Influence Score:
How these two are calculated:
The mean of Article Influence Score for each article is 1.00. A score greater than 1.00 indicates that each article in the journal has above-average influence. A score of less than 1.00 indicates that each article in the journal has below-average influence.
► The advantage of Eigenfactor Score and Article Influence Score
They allow comparison across subject disciplines.
Scholarly references join journals together in a vast network of citations. The Eigenfactor score and the Article Influence score are calculated by the structure of the entire network (instead of purely local citation information) to evaluate the importance of each journal so it automatically accounts for the differences in citation activities across subject disciplines and allows better comparison across research areas.
They are more suitable for research areas which take a longer time to have citation activities.
In many research areas, articles are not frequently cited until several years after publication. The Eigenfactor score and the Article Influence score are calculated based on the citations received over a five year period, thus it may be more applicable to the research areas which take a longer time to accumulate citation activities.