1.

How do I interpret a journal's Eigenfactor™ score?

A journal's Eigenfactor score is our measure of the journal's total importance to the scientific community.

With all else equal, a journal's Eigenfactor score doubles when it doubles in size. Thus a very large journal such as the Journal of Biological Chemistry which publishes more than 6,000 articles annually, will have extremely high Eigenfactor scores simply based upon its size.

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.

2.

How do I interpret a journal's Article Influence™ score?

A journal's Article Influence score is a measure of the average influence of each of its articles over the first five years after publication.

Article Influence score measures the average influence, per article, of the papers in a journal. As such, it is comparable to Thomson Scientific's widely-used Impact Factor. Article Influence scores are normalized so that the mean article in the entire Thomson Journal Citation Reports (JCR) database has an article influence of 1.00.

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.

3.

Do Eigenfactor™ scores and Article Influence™ scores take journal subscription prices into account?

We do not use journal subscription prices when computing the Eigenfactor and Article Influence scores. However, we do display journal price information on the journal details pages, and our cost effectiveness search ranks journals according to the value-per-dollar that they provide.

4.

What are the Eigenfactor™ field categories, and how do they compare to Thomson's JCR field categories?

In short, the Eigenfactor categories come from our efforts to map the structure of science: http://www.eigenfactor.org/map/maps.htm.

The Eigenfactor categories differ from the Thomson ISI categories in a number of ways. For one thing, the Eigenfactor categories form a hard partition in which each journal belongs to only one category, whereas the Thomson categories form a soft partition in which journals are allowed multiple category membership.

Second, our approach to mapping the structure of science is not to use our preconceived notions about what the structure of clusters or "fields" within science should be, but rather to let the data - in our case, citation patterns - tell us what the clusters or fields are. In other words, we are interested in mapping science according to what researchers do, not what they say that they do or how they self-identify. One interesting consequence of this approach is that the fields vary widely in size according to their citation behavior. Some fields, such as Tribology (the study of friction) are very small and comprise only a few journals; others fields are very large and contain multiple subdisciplines that might typically be considered separate. For example, the Molecular Biology cluster on our map includes genetics, developmental biology, microbiology, and biochemistry - areas that might be in different departments or even different colleges at many universities.

Because the Thomson categories may be preferable to the Eigenfactor categories for some purposes, we list both, and we allow search by Thomson category from the advanced search page.

5.

Where do you get your data?

The citation data used at Eigenfactor come from Thomson Scientific's Journal Citation Reports (JCR). Information about subscription prices comes primarily from journalprices.com.

At present, we have full data only for those journals listed in the JCR. The JCR provides detailed information about the nearly 7,000 journals in the sciences and social sciences which are indexed in Thomson's Web of Science citation database. Journals in the sciences and social sciences. In addition, we are able to assign Eigenfactor scores to more than 100,000 reference items that are cited by the JCR-listed journals.

6.

Are your algorithms and methods proprietary?

No. Bibliometric analysis is scientific only to the degree that it is open and replicable. Thus all of the algorithms and methods used to compute Eigenfactor score, Article Influence score, and the other statistics presented on this website are described on our methods page and laid out in full detail in our technical paper. The mapping algorithms and related methods are described on our mapping page and detailed in Rosvall and Bergstrom (2007).

7.

Why isn't my journal ranked by Eigenfactor™ score? How can I get it listed?

The journal citation data for the Eigenfactor website come from Thompson Scientific's Journal Citation Reports (JCR) for each year 1995-2006. Thus, to be listed on the Eigenfactor website, a journal either must be listed in the JCR or, minimally, be cited in the last 5 years by some journal that is listed in the JCR. At present, we have no other means for facilitating inclusion in the Eigenfactor database.

Note that the Eigenfactor website does not list as "ISI journals" those publications that are smaller than a threshold size of 12 articles per year averaged over 5 years, nor does the Eigenfactor website list those journals that do not cite other journals listed in the JCR. This is because the network centrality methods that we use to compute Eigenfactor scores are highly volatile for barely-connected nodes and for small journal sizes.

8.

The price/publisher/starting year/etc. is listed incorrectly for my journal. How can I fix it?

Send an email to cbergst@u.washington.edu and we will make the corrections as soon as possible.