For more than 40 years, scientists, editors, and librarians have used journal impact factors to compare the relative importance of journals. During this time, the use of impact factors evolved from a tool to assess journals into a means of also evaluating articles and their authors. As journal impact factors were incorporated into formulas to rate institutions and allocate research funding, they became closely scrutinized and subject to lively debate. In a 2005 editorial, the journal Nature questioned the practice of applying impact factors to individual articles by noting that 89% of their recent citations came from 25% of their published papers, and the great majority of their papers received fewer than 20 citations.

Commentaries in the May 2008, issue of Epidemiology highlighted several problems with the calculation of impact factors even when used for their intended purpose of evaluating journals:

• Only certain journals count as sources of citations, and selection of these journals is biased.
• Figures used in the numerator and denominator of the equation are not of the same logical type.
• Calculation of impact factors is not transparent or reproducible.

In December 2007, the SCImago Journal & Country Rank (SJR) database was launched as an alternative. This database uses a ranking algorithm similar to Google's PageRank method to determine a journal's impact. The SJR algorithm takes into account where a journal's citations come from and assigns greater weight to citations from journals with greater "prestige" as measured by the citing journals' SJR ranks. A popular journal cited frequently by journals of lower prestige could have a relatively high impact factor and a low SJR ranking.

Other differences between impact factors and SJR rankings include:

• Impact factor citation data comes from the Web of Knowledge database (9,000 journals) and SJR citation data comes from the Scopus database (15,000 journals).
• SJR rankings are available for free (open access); however, data only covers 1996 to the present.
• The SJR algorithm uses three years of citation data (compared to two years for impact factors) and eliminates journal self-citations.
• The SJR ranking of a journal is more difficult to manipulate than its impact factor, but the SJR methodology has not been independently validated.
• The SJR database provides additional analytics such as the ability to sort journal and country rankings by total citations, self citations, h-indexes, and 300 subject categories.

The Journal Citation Reports database containing impact factors is listed in the Core Databases section of the library's Databases Web page: http://www3.mdanderson.org/library/databases/databases.html. The SCImago Journal & Country Rank database can be accessed at http://www.scimagojr.com/. Recent publications about the SCImago Journal & Country Rank database include:

• Butler, D. "Free journal-ranking tool enters citation market," Nature, 451, 6, 2008. Published online January 2, 2008, http://www.nature.com/news/2008/080102/full/451006a.html, (doi:10.1038/451006a).
• Falagas, M.E., et al. "Comparison of SCImago journal rank indicator with journal impact factor," FASEB Journal, Published online April 11, 2008, http://www.fasebj.org/cgi/content/short/fj.08-107938v1, (doi: 10.1096/fj.08-107938).

If you need assistance with locating Impact Factors or would like to discuss alternative metrics for determining impact, please email the expert searchers at the Research Medical Library at RML_Help@mdanderson.org  

In hopes of reaching even more staff who wish to learn about EndNote, the Research Medical Library has worked with the Academic Technology Services to create a new online tutorial, EndNote Basic Skills.

This tutorial is arranged into four units: Organizing References, Creating the Library, Entering References into Word Documents, and Finishing Your Document. An assessment is provided at the end of the course and a score of 75% is required for successful completion in the Education Center. Estimated time to complete the course is 1.5 – 2.5 hours. Audio and captions are included with this tutorial.

To access the tutorial login into the Education Center: http://educationcenter.mdanderson.org/Saba/Web/Main and search for EndNote.

Please send any questions or comments to Stephanie Fulton (sfulton@mdanderson.org) or call 713-563-1722.

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