There is an increasing number of measurements of the impact of journals and their articles. Most of these are based, in some way, on the level of citations but there are many different models now in use. We list below some of the more established ones and we plan to extend this list as and when newer metrics become available in order to give the fullest possible picture of our journals' performance.
The Royal Society is a signatory of the San Francisco Declaration on Research Assessment (DORA). This declaration challenges the role played by the Impact Factor as the main means for evaluating science, and promotes the assessment of research on its own merits rather than on the basis of the journal in which the research is published.
JCR metrics
2016 Journal Citation Reports (Clarivate Analytics)
IMPACT FACTOR
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7.8 |
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Impact Factor: a measure of how often an average article in a journal has been cited. The impact factor of a journal is calculated by dividing the number of current year citations to source items published in that journal during the previous two years.
5-Year Journal Impact Factor: as above, but uses citations to articles from the most recent five full years.
Immediacy index: the average number of times that an article is cited in the same year it is published.
Citation distribution: the distribution of citations to articles over the previous two years that contributes to the current year’s impact factor:
EIGENFACTOR
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0.06960 |
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2.862 |
Eigenfactor: an estimate of the percentage of time that library users spend with that journal. The Eigenfactor algorithm corresponds to a simple model of research in which readers follow chains of citations as they move from journal to journal. It ignores self-citations. For further information see http://www.eigenfactor.org.
Article influence: a measure of the impact of a journal as a whole on the rest of the literature. It is the fractional contribution of a journal to the total Eigenfactor divided by the fractional contribution of journal to the total articles published.
Scopus metrics
The SCImago Journal Rank is very much like the Eigenfactor except that it is based on the larger Scopus dataset. It expresses the average number of weighted citations received in the selected year by the documents published in the selected journal in the three previous years, i.e. weighted citations received in year x to documents published in the journal in years (x-1), (x-2) and (x-3).
Source Normalized Impact per Paper (SNIP): measures contextual citation impact by weighting citations based on the total number of citations in a subject field. The impact of a single citation is given higher value in subject areas where citations are less likely, and vice versa.
Further information on Scopus metrics can be found here.
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