The document provides information about how Journal Impact Factors are calculated. It defines Journal Impact Factor as the average number of times articles from a journal published in the last two years were cited in the current year. It then explains the formula used to calculate Journal Impact Factors and visualizes the calculation process. The document also addresses common questions about what is included in the numerator and denominator and how title changes, supplements, and self-citations are handled in the calculation.

1. Journal Impact Factor
3-year calculationwindow – 2016, 2017, and 2018
Document published March 2019

2. A note on these slides Common queries1 5
Definition: Journal
Impact Factor
JCR journal
suppression
2 6
Journal Impact Factor
calculation (formula)
Further reading3 7
Journal Impact Factor
calculation (visual)
Contact information4 8
Agenda
2

3. A note on these slides
3
The information herein applies to the Journal Impact Factor
calculation for 2018, as published in the June 2019 Journal Citation
Reports (JCR).
Publishers can contact the Publisher Relations team with questions:
publisher.relations@clarivate.com

4. Definition: Journal Impact Factor
4
Journal Impact Factor is a journal-level metric; it is the average
number of times a journal’s articles – specifically, those published in a
2-year period – were cited in 2018.
Journal Impact Factors are calculated for journals selected for and
indexed in the Science Citation Index Expanded (SCIE) or the Social
Sciences Citation Index (SSCI) of Web of Science.
Journal Impact Factors are published annually in the Journal Citation
Reports (JCR).
https://clarivate.com/products/journal-citation-reports/

5. Journal Impact Factor calculation (formula)
5
• A = the journal’s total citations in 2018
• B = 2018 citations to all items published in 2016-17
• B is a subset of A
• C = the number of citable items the journal published in 2016-17
• D = B/C = 2018 Journal Impact Factor
A Journal Impact Factor of 1.0 means that, on average, articles published 1 or 2 years ago were
cited one time in 2018.
C= DENOMINATOR
2018 Citations
to All Items Published
in the Previous 2 Years
(2016, 2017)
The Number of Citable Items Published
During the Previous 2 Years
(2016, 2017)
B=NUMERATOR

6. Journal Impact Factor calculation (visual)
6
201820172016
Citations
2018 publication
2016 or 2017 publication
All
Previous
Years
2015 2019
2018
Journal Impact Factor
published in
June 2019 JCR
2018 Journal Impact Factor =
2018 citations to all items published in 2016 and 2017
Total # citable items published in 2016 and 2017

7. Common Queries

8. What’s in the numerator?
8
Citations are drawn only from the Web of Science Core Collection:
• Science Citation Index Expanded (SCIE)
• Social Sciences Citation Index (SSCI)
• Arts & Humanities Citation Index (AHCI)
• Emerging Sources Citation Index (ESCI)
• Conference Proceedings Citation Index (CPCI)
• Science edition
• Social Sciences and Humanities edition
• Book Citation Index
• Science edition
• Social Sciences and Humanities edition
— Citations are not drawn from any other Web of Science index (BIOSIS, Zoological Record, etc).

9. What’s in the denominator?
9
• Citable items are in the denominator.
• Citable items are defined as materials indexed in Web of Science as articles, reviews,or
proceedings papers.
• Items with any other document type -- including editorial material, news items, and meeting
abstracts, among others -- are not included in the denominator.
• Each section of each journal is evaluated individually.
– For example, the Letters section in one journal might be citable items (eg, those in Nature) but a section with the
same name in another journal can be deemed non-citable.

10. Characteristics of a citable item
10
• Abstract
• Descriptive article title
• Named author(s) with address/affiliation information
• Funding information
• Article length
• Cited references
• Data content

11. Title changes and Journal Impact Factor
11
How do title changes affect JournalImpact Factor?
Year 1 • The new title is listed with an Immediacy Index: citationsin the
JCR year (2018) to contentpublished in the JCR year (2018).
• The old title is listed with JournalImpact Factor.
Year 2 • The JCR lists Journal Impact Factors for both the new and the
old titles.
• Publishers can promote a single, combined JIF, but the JCR will
list the statistics separately.
Year 3 • The old title is no longer listed.
• The new title appearswith a Journal Impact Factor.

12. Supplements and Journal Impact Factor
12
How are supplementsand special issues handled?
• Citable items from these publications are counted in the denominator.
• Ensure that Publisher Relations is aware of these issues, especially if they fall
outside the stated frequency of the journal.

13. Table of Contents and Journal Impact Factor
13
My journal added a new section over the past2 years. Is this change captured in the JCR?
• Adding new sections or changing existing sections in a currently indexed journal can
affect the Journal Impact Factor.
• Alert Publisher Relations to such changes: publisher.relations@clarivate.com

14. Title variants and Journal Impact Factor
14
Researchers citemy journal’s name inconsistently. Is the JCR still capturing the citations?
• Yes. Title variants are unified by the JCR team.
• A citation must include the correctjournal title (or JCR-accepted variant) and the correct
year to be calculated for the Journal Impact Factor.
• Publishers are encouraged to provide clear instructions on how to cite the journal,
especially for “online first” or “publish ahead of print” versions of articles.

15. How to cite the JCR
15
• JCR has a data year and a copyright year.
– The data year is the Journal Impact Factor year.
– The copyright year is separate but relevant for proper citation.
• The 2018 Journal Impact Factor will be published and copyrighted in 2019.
• It should be cited as:
2018 Journal Citation Reports (Clarivate Analytics, 2019)

16. JCR Journal Suppression

17. JCR journal suppression
17
• Increasingly rare but still enforced
• Action primarily taken in response to excessive self citation and citation stacking
• Suppression is not de-selection; journals can remain indexed in Web of Science

18. Journal Self-Citation: Suppression of individual journals
18
What the suppressedJournal metricswouldlook like • Characteristics of suppressed journals:
• High percentage of journal self-citations in
Journal Impact Factor numerator
• Large proportional increase in Journal
Impact Factor with/without journal self-
citations
• Large effect of journal self-citations on
rank in category by Journal Impact Factor
• Journals in bottom 10% ranking by total
citations and/or by JIF are not suppressed
• Suppressed journals represent extreme
outliers in citation behavior
• Science Edition and Social Sciences Edition
are analyzed separately
• Journals are suppressed for one year, and
re-evaluated with the next year’s data.

19. Citation Stacking: Donor and Recipient Journal Pair Suppression
19
What the suppressedJournal metricswouldlook like
• Characteristics of suppressed journals:
• Donor provides a high percentage of Recipient’s Total
Citations
• Donor provides a high percentage of Recipient’s Journal
Impact Factor numerator citations
• Donor citations are concentrated in Journal Impact
Factor numerator
• Journals in bottom 10% ranking by total citations and/or
by Journal Impact Factor are not suppressed
• Suppressed journals represent extreme outliers in
citation behavior
• Science edition and Social Sciences edition are analyzed
separately
• One-year suppression may apply to both Donor and
Recipient journals; both will be re-evaluated with the
next year’s data.

20. Further reading
20
Hubbard SC, McVeigh ME. Casting a wide net: the Journal Impact Factor numerator. Learned
Publishing. 2011;24(2):133-7. http://dx.doi.org/10.1087/20110208
McVeigh ME, Mann SJ. The Journal Impact Factor Denominator: Defining Citable (Counted) Items.
JAMA. 2009;302(10):1107-9. http://jama.jamanetwork.com/article.aspx?articleid=184527
The ClarivateAnalyticsImpact Factor
https://clarivate.com/essays/impact-factor/
The History and the Meaning of the JournalImpact Factor
https://clarivate.com/essays/history-journal-impact-factor/

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