Journal Impact Factor (and other scientometric indicators)
The Journal Impact Factor (JIF) determined by Thomson Reuters is currently the most established and widely used scientometric/bibliometric indicator at journal level.
The JIF is a measure of how frequently articles published in a particular journal are cited on average in the two years following publication. The greater the value, the more influential the journal. However, the value range differs greatly depending on the field of research.
The previous year’s results are published annually (around the middle of the year) in the Journal Citation Reports.
SCImago Journal Ranking, Source Normalized Impact per Paper and Impact per Publication are three further well-established scientometric indicators on journal level. They are based on the Scopus data. Each summer, the figures for the previous year are released.
SCImago Journal Ranking (SJR) accounts for both the number of citations received by a journal and the importance of the journals where such citations come from. SJR computation uses an algorithm similar to Google PageRank.
Source Normalized Impact per Paper (SNIP) measures contextual citation impact by weighting citations based on the total number of citations in a subject field. SNIP is defined as the ratio of a journal's citation count per paper and the citation potential in its subject field. It aims to allow direct comparison of sources in different subject fields.
Impact per Publication (IPP) measures the ratio of citations in a year (Y) to scholarly papers published in the three previous years (Y-1, Y-2, Y-3) divided by the number of scholarly papers published in those same years (Y-1, Y-2, Y-3).
> SJR, SNIP and IPP values 2015