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Metrics: Journal Bibliometrics

Common Metrics

Impact Factor
The Impact Factor is defined as the average number of times that articles published in the journal in the past two years have been cited in the current year. For example, a journal with an Impact Factor of 30 in 2012 means that the articles published in 2010 or 2011 have each been cited on average 30 times in 2012.

SCImago Journal Rank (SJR)
The SJR is based on a number of citations received by number of articles published calculation which covers three years. However, the citations are weighted depending on the prestige and subject area of the journal. For example, citations from a journal with high prestige in its field have a high value and citations in a subject area where there are abundant citations such as medicine have a low value.

Source-Normalized Impact per Paper (SNIP)
The SNIP is calculated by dividing the underlying citations received by number of articles published figure by the Citation Potential of the subject area. The Citation Potential is essentially the likelihood of being cited, for example, a subject area with a high likelihood of being cited such as life sciences will have a high Citation Potential and a subject area with a low likelihood of being cited such as history will have a low Citation Potential.

Eigenfactor
The Eigenfactor is similar to the SJR because citations recieved are weighted by the prestige of the citing journal. However, the Eigenfactor is calculated using Web of Science rather than Scopus data, self-citations are excluded, and citations are counted over five years not three years.

Article Influence Score
The Article Influence Score is the average influence of a journal’s articles. It is basically calculated by dividing the Eigenfactor Score by the number of articles in the journal (mathematically adjusted so it is comparable with other journals).

Sources

Journal Citation Reports (JCR)
The Impact Factor, Eignefactor and Article Influence Score are calculated using the JCR which is produced using data from the Web of Science. The JCR contains information on over 10,000 journals but the coverage of non-English language titles is limited.

Scopus
Scopus is used to calculate the SJR and SNIP. It covers over 20,000 journal titles and 6 million conference papers and has better coverage of the social sciences and non-English language titles from Europe than the JCR.