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Metrics: Common Metrics

Author Metrics

Author metrics include:

  • Publication count - number of publications produced by an individual, department, etc
  • Citation count - number of times a publication is cited by other publications
  • h-index - devised in 2005 by Professor Jorge Hirsch, an American physicist, to measure the personal impact of researchers. It is defined as the largest number h, where a researcher has at least h publications cited at least h times. For example, someone with an h-index of 25 has written 25 papers which have each been cited at least 25 times.

Author metrics can be found in Scopus, the Web of Science and Google Scholar. Scopus includes the SciVal tool for detailed analysis. 

Journal Metrics

Journal metrics include:

  • Impact Factor - 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) - 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) 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 - 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 - 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)

The Impact Factor, Eigenfactor and Article Influence Score are calculated using the Journal Citation Reports (JCR), which is produced using data from the Web of Science. Scopus is used to calculate the SJR and SNIP.