Journal metrics attempt to quantify the research impact of a publication or authors work. Referred to as the impact factor, these calculations attempt to provide context for the scientific importance, or relevance of a journal or publication.
Traditionally, two different companies have provided journal level metric data:
The library licenses the Scopus database from Elsevier. However, both publishers have made their data freely available to third parties, who in turn have their own mathematical models they use to determine a journals impact.