The range of models used to measure the impact of journals and articles is constantly increasing, though most are based on the level of citations. As a signatory to DORA, the Royal Society offers a variety of journal and article-based metrics. We are also a member of the Initiative for Open Citations (i4OC) which is a multi-stakeholder project to make scholarly citation data openly available to enable the creation of new and better metrics.
Impact factor
2017 Journal Citation Reports (JCR) (Clarivate Analytics)
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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 by total number of published articles in the journal during the previous 2 years.
5-year impact factor: is the impact factor calculated using a base of 5 years' worth of cited articles, rather than 2 years. This gives a fairer picture of journals in fields with slower citation patterns, such as mathematics.
Immediacy index: the average number of times that an article is cited in the same year it is published.
Eigenfactor: a measure of the number of times articles from the journal have been cited in the JCR year. It is a ratio of the number of citations to total number of articles but unlike Impact Factor, it counts citations in both science and the social sciences, it eliminates self-citations (citations of articles published in the same journal) and weights each reference according to the amount of time spent reading that article. The scores are weighted so the sum Eigenfactor scores from all journals in JCR is 100.
Citation distribution: the distribution of citations to articles over the previous 2 years that contributes to the current year’s impact factor.
2017 ranking
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CiteScore: very much like the Impact Factor except that it is based on the larger Scopus dataset and uses 3 years of data. It is the number of citations received by a journal in one year to documents published in the three previous years, divided by the number of documents indexed in Scopus published in those same three years.
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.
Article usage metrics
We collect article usage statistics on a daily basis and display them on each article within the ‘Info & Metrics’ tab. The statistics comprise the number of times an article abstract, full-text and PDF view is loaded by a user from individual journal websites.
Note that all articles have zero usage upon publication and the latest available metrics will be displayed 24 hours after they have been collected.
Altmetrics
Altmetrics are non-traditional metrics proposed as an alternative to citation impact metrics.
We use a partner organisation called Altmetric to track and display the online activity around an article. Altmetric track social media sites, newspapers and magazines for mentions of each published article. The aim is to help authors quantify the attention their article is receiving and to help readers establish the articles their peers think are interesting.
The Altmetric ‘doughnut’ can be found on the ‘Info & Metrics’ tab of each article.
