Bibliometrics and Impact Factor: SNIP
This guide explains how impact factor is used and calculated in journal and article rankings, as well as other methods of citation analysis.
Paper on SNIP
- Measuring contextual citation impact of scientific journalsby Henk F. Moed, November 2009
Technical Notes
SNIP is just one type of measure created by Moed and his team.
Look in this PDF for the descriptions of the types of data represented in the Centre for Science and Technology Studies (CWTS) Journal Indicators at Leiden University.
What is SNIP?
Created by Professor Henk F. Moed at Centre for Science and Technology Studies (CTWS), University of Leiden, 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
- SNIPSNIP was developed using Elsevier (Scopus) citation data. (open access)
- Journal Metrics (by Elsevier)SNIP is also available here. (open access)
Example of CWTS Journal Indicators
Journals in the Education field from 1999 sorted by SNIP.
