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RESEARCH GUIDES

Bibliometrics and Altmetrics: Measuring the Impact of Knowledge

This guide includes information on which of the databases contain citation measures that can be used to gage either an author, article or journal impact.

DEFINITION #1: Eigenfactor

The Eigenfactor came out of the Metrics Eigenfactor Project in 2008, a bibliometric research project conducted by Professor Carl Bergstrom and his laboratory at University of Washington.

The Eigenfactor Score measures the number of times articles from the journal published in the past five years have been cited in the Journal Citation Reports (JCR) year.

Like the Impact Factor, the Eigenfactor Score is essentially a ratio of number of citations to total number of articles. However, unlike the Impact Factor, the Eigenfactor Score:

  • Counts citations to journals in both the sciences and social sciences.
  • Eliminates self-citations. Every reference from one article in a journal to another article from the same journal is discounted.
  • Weights each reference according to a stochastic measure of the amount of time researchers spend reading the journal.

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 Eigenfactor uses Thomson Reuters Web of Science citation data.

Further Reading:

Eigenfactor (EF) and Article Influence (AI)

In 2011, the journal Nature has the highest Eigenfactor score, with a score of 1.65524. The top thousand journals, as ranked by Eigenfactor score, all have Eigenfactor scores above 0.01.

DEFINITION #2: Article Influence Score

The Article Influence Score calculates measures the relative importance of the journal on a per-article basis. It is the journal's Eigenfactor Score divided by the fraction of articles published by the journal. That fraction is normalized so that the sum total of articles from all journals is 1.

The mean Article Influence Score is 1.00. A score greater than 1.00 indicates that each article in the journal has above-average influence. A score less than 1.00 indicates that each article in the journal has below-average influence.

Article Influence uses Thomson Reuters Web of Science citation data.

Access:

Article Influence Scores can be accessed freely at eigenfactor.org or through a subscription to Journal Citation Reports (JCR).

 
Article Influence scores of a journal can vary between http://www.eigenfactor.org/ and JCR, even for the same year. This may be because the eigenfactor metrics take into account some other sources, such as dissertation and newspaper citations.

Article Influence (AI) Sample

In 2011, the top journal by Article Influence score is Reviews of Modern Physics, with an article influence of 28.9002. This means that the average article in that journal has twenty eight times the influence of the mean journal in the JCR.