Bibliometrics and Impact Factor: Article Influence and Eigenfactor

This guide explains how impact factor is used and calculated in journal and article rankings, as well as other methods of citation analysis.


Article Influence Scores can be accessed freely at or through a subscription to Journal Citation Reports (JCR), which is part of Web of Science.

Variations of Citation Data

Like the Impact Factor, the Eigenfactor Score and Article Influence Score use Thomson Reuters citation data to assess and track the influence of a journal in relation to other journals in the same discipline.

Eigenfactor Metrics are available only for JCR (Journal Citation Reports) years 1995 and later. 


Article Influence scores of a journal can vary between 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.

What is Article Influence?

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.

In 2006, the top journal by Article Influence score is Annual Reviews of Immunology, with an article influence of 27.454. This means that the average article in that journal has twenty seven times the influence of the mean journal in the JCR.

Article Influence uses Thomson Reuters (ISI Web of Knowledge) citation data.

What is Eigenfactor?

The Eigenfactor came out of the Metrics Eigenfactor Project, 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 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. In 2006, the journal Nature has the highest Eigenfactor score, with a score of 1.992. The top thousand journals, as ranked by Eigenfactor score, all have Eigenfactor scores above 0.01.

The Eigenfactor uses Thomson Reuters (ISI Web of Knowledge) citation data.

Visualizing Information Flow

Paper on Eigenfactor

What's an Eigen?

An eigen is a particular or peculiar characteristic and is a prefix that can be applied to different scientific terms. For example, eigenvalue, eigenstate, etc.

Oxford English Dictionary (requires a subscription)

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