Scholarly Metrics

Overview

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:

  1. Journal Impact Factor (JIF)
  2. Find Impact Factor using Journal Citation Reports
  3. Other Metrics Available on Journal Citation Reports
  4. What is 5-year Impact Factor?
  5. What are Eigenfactor Score and Article Influence Score?

Journal Impact Factor

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

Impact Factor Numerator - Cites to recent items:

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. 

Impact Factor Denominator - Number of recent items:

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. 

For example,

  • Impact Factor of 1.0 means that, on average, the articles published one or two years ago have been cited one time.
  • Impact Factor of 2.5 means that, on average, the articles published one or two years ago have been cited two and a half times.

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.

Notes

  • Citation practices vary between disciplines, so Journal Impact Factors should NOT be used to compare journals across different subject areas.
  • Journal Impact Factors cannot assess the quality of individual articles.
  • Not all journals have an Impact Factor - they must be indexed in Journal Citation Reports, which covers journals listed in Science Citation Index (SCI) and/or Social Sciences Citation Index (SSCI) of Web of Science.

Find Impact Factor using Journal Citation Reports

1 - Search by Journal Title

  • Step 2. Type in the journal title and click the search icon.

  • Step 3.  The page displays JIF for the current year. You can see for all year by clicking on All Years.

2 - Search by Subject Category

  • Step 1Go to Web of Science > Journal Citation Reports
  • Step 2. Click " Browse by Category"
  • Step 3. Click Select Categories”  to display the different categories
  • Step 4. Select a subject category (or multiple categories), e.g. Chemistry, Appliedand click "Submit".

  • Step 5. Click on the number of journals for the year of interest to display the JIF for the category

 

Other Metrics Available on Journal Citation Reports

Apart from Journal Impact Factor, Journal Citation Reports provide other metrics such as 5-year Impact FactorEigenfactor ScoresArticle 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.

What is 5 year Impact Factor?

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.

What are Eigenfactor Score and Article Influence Score?

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.

Eigenfactor Score:

  • measures the number of times articles from the journal published in the past five years have been cited in the JCR year.
  • considers which journals have contributed these citations so that highly cited journals will have more influence than lesser cited journals.
  • With Eigenfactor Scores, references from one article in a journal to another article from the same journal are removed ( journal self-citation is excluded).

Article Influence Score:

  • determines the average influence of the journal's articles over the first five years after publication.
  • is calculated by multiplying the Eigenfactor Score by 0.01 and dividing by the number of articles in the journal, normalized as a fraction of all articles in all publications.
  • is roughly analogous to the 5-Year Journal Impact Factor in that it is a ratio of a journal’s citation influence to the size of the journal’s article contribution over a period of five years. 

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.