Sciences - Citations Resources and Guidelines: Impact Factors

"An Impact Factor is one measure of the relative importance of a journal, individual article or scientist to science and social science literature and research. Each index or database used to create an impact factor uses a different methodology and produces slightly different results, revealing the importance of using several sources to judge the true impact of a journal's or scientist’s work. Included on this page is information on Journal Impact Factor, Author Impact Factor, and Article Impact Factor.

Informed and careful use of these impact data is essential, and should be based on a thorough understanding of the methodology used to generate impact factors. There are controversial aspects of using impact factors:

• It is not clear whether the number of times a paper is cited measures its actual quality.
• Some databases that calculate impact factors fail to incorporate publications including textbooks, handbooks and reference books.
• Certain disciplines have low numbers of journals and usage. Therefore, one should only compare journals or researchers within the same discipline.
• Review articles normally are cited more often and therefore can skew results.
• Self-citing may also skew results.
• Some resources used to calculate impact factors have inadequate international coverage.
• Editorial policies can artificially inflate an impact factor.

Eigenfactor (URL: http://www.eigenfactor.org/ )

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.