The Eigenfactor is another way that the impact of journals is measured (www.eigenfactor.org). It is based on an algorithm that evaluates the networks between journals. The Eigenfactor attempts to calculate a percentage estimate of the total time that all journal users spend with that journal compared to all other journals. The numbers are normalized so that the total of all Eigenfactors is 100.
Eigenfactor ranks and maps scientific knowledge:
· Ranks journals similar to Google ranking of websites. It uses the structure of the entire network (instead of purely local citation information) to evaluate the importance of each journal. Journals are rated according to the number of incoming citations, with citations from highly-ranked journals weighted to make a larger contribution to the Eigenfactor than those from lesser-ranked journals.
· Eigenfactor Metrics consist of the Eigenfactor score and the Article Influence score.
o Eigenfactor score: a measure of the overall value provided by all of the articles published in a given journal in a year.
o Article Influence score: a measure of a journal’s prestige based on per article citations and comparable to Impact Factor.
· Measures journal price as well as citation influence. The Cost-Effectiveness Search orders journals by a measure of the value of the dollar they provide.
· Ranks scholarly journals as well as newspapers, theses, popular magazines, etc.
· Adjusts for citation differences across disciplines, allowing for better comparison across research areas.
· Calculations are based on the citations received over a 5-year period vs. 2 years in JCR.
· Available free of charge on the web at eigenfactor.org
How to find the Eigenfactor:
1. Go to eigenfactor.org
2. Search for a single journal name or choose a subject category
3. Select a year
4. Click Search
Note: The Eigenfactor and the Impact Factor for a journal can also be found in Journal Citation Report. If you don't need the mapping feature of Eigenfactor.org to show, for example, the interconnectivity of the journals to each other, then the eigenfactor score from JCR will be more current. An example of the mapping is presented in the screen shot below.
Searching the site eigenfactor.org for the journal Nature Cell Biology.
Eigenfactor.org's uses the data from ISI. As part of their agreement with ISI, they use data that is one year old. If the latest ISI data on JCR is 2011, then the Eigenfactor.org data is from 2010. Which means if you want the data to match, use data on the JCR site that is one year older than the current year.
Searching ISI's Journal Citation Reports for the journal Nature Cell Biology. The following quote is taken from ISI's JCR website:
"The Eigenfactor Score calculation is based on the number of times articles from the journal published in the past five years have been cited in the JCR year, but it also considers which journals have contributed these citations so that highly cited journals will influence the network more than lesser cited journals. References from one article in a journal to another article from the same journal are removed, so that Eigenfactor Scores are not influenced by journal self-citation."
The screen-shot below is the current year data from ISI for that journal.