Measuring Scholarly Research Impact: Journal Impact Using Citations

- Impact Factor

What It Is: a way to measure the relative impact of a journal within its field by determining the average number of citations an article published in the journal receives over a set period of time.

How To Calculate: 2010 Impact Factor is A/B where A = Citations made in 2010 for articles published from 2008-2009 and B = number of articles published from 2008-2009.

Example: Nature (2010) = 36.104, New England Journal of Medicine (2010) = 53.486, JAMA (2010) = 30.011

Citation: http://thomsonreuters.com/products_services/science/free/essays/impact_factor

- Eigenfactor

What It Is: similar to Impact Factor, but this also takes into account the 'impact' of the journals citing the articles in your journal of interest - i.e., are the articles in your journal of interest being cited in high impact or low impact journals?

How To Calculate: complicated calculation, performed by Eigenfactor.org

Example: Nature (2010) = 1.73, New England Journal of Medicine (2010) = 0.69, JAMA (2010) = 0.31

Citation: http://www.eigenfactor.org/methods.htm

- SCImago Journal Rank (SJR)

What It Is: similar to Eigenfactor -  takes into account the 'impact' of the journals citing the articles in your journal of interest - i.e., are the articles in your journal of interest being cited in high impact or low impact journals?

How To Calculate: complicated calculation, perfromed by Scopus

Example: Nature (2010) = 13.4, New England Journal of Medicine (2010) = 9.1, JAMA (2010) = 4.8

Citation: Gonzalez-Pereira, B., Guerrero-Bote, F.V., & Moya-Anegon, F. (2009) "The SJR Indicator: A New Indicator of Journals' Scientific Prestige". Available at: http://arxiv.org/abs/0912.4141

- Source Normalized Inpact per Paper (SNIP)

What It Is: similar to impact factor but with citations being 'normalized' to account for differences in citation patterns among different fields of study

How To Calculate: complicated calculation, performed by Scopus

Example: Nature (2010) = 8.1, New England Journal of Medicine (2010) = 13.56, JAMA (2010) = 9.5

Citation: Leydesdorff, L. & Opthof, T. (2010) "Scopus's Source Normalized Impact per Paper (SNIP) versus Journal Impact Factor Based on Fractional Counting of Citations". Available at: http://arxiv.org/abs/1004.3580