Journal Metrics

As journal metrics become more and more important for scientists and their institutions, Copernicus Publications decided to show the four most important ones. A short explanation is listed below. For further information please visit the individual websites of Thomson Reuters and SCOPUS.

It is important NOT to compare the different journal metrics as the results apply from different calculations. As a comparison the 2009 journal metrics for "Nature Geoscience" are listed:

Thomson Reuters Impact Factor

The annual Journal Citation Report Impact Factor is a ratio between citations and recent citable items published. Thus, the impact factor of a journal is calculated by dividing the number of current year citations to the source items published in that journal during the previous two years.

The 5-year impact factor is calculated by expanding the counted articles to the previous five years.

Source: Thomson Reuters

SCOPUS SNIP

The 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.

SNIP

• Measures contextual citation impact by "normalizing" citation values;
• Takes a research field's citation frequency into account;
• Considers immediacy – how quickly a paper is likely to have an impact in a given field;
• Accounts for how well the field is covered by the underlying database;
• Calculates without use of a journal's subject classification to avoid delimitation;
• Counters any potential for editorial manipulation.

Source: SCOPUS

SCOPUS SJR

The SCImago Journal Rank (SJR) is a prestige metric based on the idea that "all citations are not created equal". With SJR, the subject field, quality and reputation of the journal has a direct effect on the value of a citation.

SJR

• Is weighted by the prestige of the journal, thereby "leveling the playing field" among journals;
• Eliminates manipulation: raise the SJR ranking by being published in more reputable journals;
• "Shares" a journal's prestige equally over the total number of citations in that journal;
• Normalizes for differences in citation behavior between subject fields.

Source: SCOPUS