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Impact Metrics

What is the Journal Impact?

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Several indicators evaluate the impact or reputation of a journal. They are based on the number of citations of a journal over a specific period of time.

It can be useful to identify:

  • The most renowned titles in a field
  • Current strategic research topics
  • In which journals to publish

Keep in mind:

  • The period covered by these indicators is of 3-5 years which is too short for the social sciences, whose impact is longer
  • Invisibility: journals that publish in small niche research areas will not appear
  • High quality articles in non-English journals are less cited
  • Many journal impact indicators do not take the subject field into account
  • Impact manipulation: some editors ask authors to either cite titles they own or to cite other editors with whom they have agreements
  • To evaluate the research of an author, do not forget to consider other indicators, such as the h-index, in addition to journal impact indicators

Journal Impact Indicators

The calculation of the Impact factor (IF) for a journal in the current year :

Total number of citations received by a journal in a given year (ex: 2022)
by all content published in the last two years (ex: 2020-2021)

Impact Factor =   ____________________________________________________________________________________________

Total number of articles & reviews published in a journal between the last 2 years (ex: 2020-2021)

A five-year coverage impact factor also exists.

Source of data: the IF is based on data from the Web of Science Core Collection database (owned by Clarivate Analytics). This metric is updated once a year in June.

Where to find this indicator:

Keep in mind the Impact Factor:

  • Is the oldest and most used journal indicator
  • Does not take the subject field into account
  • Does not eliminate self-citations

Eigenfactor is the average number of citations a journal has received over the last 5 years in the Journal Citation Reports. The two main differences between the Impact Factor and the Eigenfactor are:

  • Eigenfactor eliminates self-citation
  • It weights journal impact factors taking into account how often a journal will be used by researchers

Eigenfactor scores are scaled so that the sum of the Eigenfactor scores of all journals listed in the Journal Citation Reports (JCR) is 100. The top thousand journals have an Eigenfactor above 0.01 and a journal like The American Economic Review, which has been in the top 10 journals in social sciences, could reach an Eigenfactor of 0.09701.

Source of data: Web of Science Core Collection (owned by Clarivate Analytics)

Where to find this indicator:

Keep in mind Eigenfactor:

  • Eliminates the problem of self-citations
  •  Takes the prestige of a journal into account

SCimago Journal Rank measures the average number of citations for a journal over the last 3 years. Subject field, quality and reputation of journals are taken into account to weight citations, using an algorithm similar to Google's Page Rank. It can be applied to journals, book series and conference proceedings.

Average # of weighted citations received in a year

SCimago Calculation =   _________________________________________________________________________________________

Total number of articles & reviews published in a journal between the last 2 years (ex: 2020-2021)

Source of data: Scopus database (owned by Elsevier).

Where to find this indicator:

Freely accessible through Scimago

Keep in mind Scimago:

  • Takes the reputation of a journal into account

The SNIP is the average number of citations for a journal over the last 3 years. This metric weights citations based on the citation patterns in a subject field.

Source of data: Scopus database (owned by Elsevier)

Where to find this indicator:

Keep in mind SNIP:

  • Takes the subject field into account. It allows the comparison of different fields (example: anthropology and political & international relations)

CiteScore is an open metric, developed in 2016, calculated as follows:

Citations in a year to documents published in previous 3 years

CiteScore calculation =           _________________________________________________________________________

# of documents published in previous 3 years

This indicator is calculated in the same way as the Impact Factor but it has two main differences from this last one:

  • It takes into account all items published in a journal (or serial publication) indexed in the Scopus database, whatever the nature of the item (research article, review, letter to the editor, editorial, erratum, conference paper, etc). In contrast, the IF considers certain types of articles (research articles, summaries, notes, short communications) to be suitable for citation.
  • It's calculated for a period of 3 years.

Source of data:  CiteScore is calculated based on Scopus database (Elsevier).

Where to find this indicator:

Keep in mind CiteScore:

  • Does not eliminate self-citations
  • Does not take into account the subject field
  • Considers all types of items published in a journal as suitable for citation
  Eliminates self-citation Journal reputation Subject Field Open metric
Impact Factor no no no no
Eigenfactor yes yes no no
Scimago no yes no yes
SNIP no no yes yes
CiteScore no no no yes

Comparison of databases

Scopus contains more titles in the Social Sciences than Web of Science; Nevertheless, in both databases, English journals are overrepresented.