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Impact Metrics

What is the Journal Impact?

Original illustration: ColiN00B, pixabay license

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 journal X in 2017

 

Total number of citations received by journal X in 2017 by all content published in 2015-2016 (last 2 years)

Impact Factor =   ____________________________________________________________________________________________

Total number of articles & reviews published in journal X  between 2015-2016 (last 2 years)

 

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)

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 Thomson's Journal Citation Reports (JCR) is 100. The top thousands 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 citation
  • This indicator takes the prestige of a journal into account

Scimago measures the average number of citations for a journal over the last 3 years. It takes the quality and reputation of journals into account, using an algorithm similar to Google's Page Rank.

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

Where to find this indicator:

Scimago: freely accessible

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)
  Eliminates self citation Journal reputation Subject Field
Impact Factor no no no
Eigenfactor yes yes no
Scimago no yes no
SNIP 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 over represented.

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