Saturday, 8 November 2008

Eigenfactor, SCImago, Journal Rankings and the PageRank algorithm

PageRank is a trade mark of Google, and describes the process by which Google ranks pages using hyperlinks to web pages. The same process can be used to rank journals and collections of journals using citations. It helps to understand the basic principles of page ranking to interpret journal ranking tools that use the same principles. There is a very accessible article on Wikipedia about PageRank.

Two substantial websites that rank journals in this way, Eigenfactor using Thomson Scientific's Journal Citation Reports (JCR) data and SCImagio using SCOPUS data.

Eigenfactor.org

Eigenfactor generates two measures the Eigenfactor Score and an Article Influence measure. You can search for individual titles and groups of titles by subject category to achieve a ranking of journal titles. Each measure is presented as a graphic representing changes in the value over time.

Eigenfactor Measure. 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, with a score of 1.992. The top thousand journals, as ranked by Eigenfactor, all have Eigenfactors above 0.01. (Eigenfactor.org FAQ)

Article Influence measure. 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 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 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 (Eigenfactor.org FAQ).


Eigenfator also has a mapping function showing the flows of citations between discipline/subjects areas, and the volume of publication within each discipline/subjects area. Eigenfactor inherits the subject structure of JCR, with some differences for example in the Eigenfactor data journals can only belong to one subject area.

SCImago

SCImago has similar functions to Eigenfactor.org but with a geographical component, statistics generated by country and region, and a much broader selection of 19 measures. These include familiar measures such as the h-index and SCImago's unique ranking SJR. SCImago has the capability to compare indicators by region or country (USA comes top of most tables followed by UK, Germany and Japan) as well as compare groups of journals and select individual titles. Each measure is presnted graphically. Basic functions are:

  • Journal Indicators

  • Journal Search (Search for individual titles)

  • Country Indicators

  • Country Search (clickable map)

  • Compare (countries and regions)

  • Map Generator (co-citation and bibble charts)


Both websites are free to access.

Links

Journal Citation Reports. Requires an ATHENS User Name and Password.
Short list of Journal Ranking websites
SCOPUS. Requires an ATHENS User Name and Password, off-campus.

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