The following metrics are based on the Scopus bibliography database provided by Elsevier. Since the full citation data is available from 1996, the journal impact metrics are available from 1999.
SCImago Journal Rank (SJR)
SJR was developed by SCImago research group headed by Felix de Moya at University of Granada. SJR is nothing but the prestige metric which is derived iteratively using the other citing journals. If the journal is cited by the high prestige journal then its SJR value will be high and vice-versa.
For example: Every journal shares its prestige equally among its citation. Consider a computer science journal with a long list of references, is having a high impact as well as a lot of citations. In that case, the prestige of high impact will be shared among the lots of citations, consecutively each citation has low value in its field.
On the other, consider a social science journal tends to have a small list of references, may have low impact factor with less number of citations. So, the prestige of low impact will be shared among less number of citations, consecutively each citation has high value in its field.
SJR = Weighted citation/Number of documents published
This calculation is useful to normalize the citation behaviour while comparing the SJR of journals of different subject fields.
Source : https://www.elsevier.com/editors-update/story/journal-metrics/
Source Normalized Impact per Paper (SNIP)
SNIP was developed by Henk Moed and CWTS group at University of Leiden, Netherlands in 2010 and used to calculate the contextual citation impact. This is used to improve the differences in the popularity of the different scientific fields by taking into consideration the citation potential of a journal. SNIP is calculated into two steps: first is to calculate impact factor, which we have already discussed in the previous blog and next is the citation potential. The citation potential reflects that how highly you being cited by the journal in the particular field. Suppose we want to calculate the citation potential of journal “ABC” for 2016. The SNIP calculation steps are:
- Collect all the papers of 2013-15, cite the papers of the journal “ABC” in 2016.
- Take a look at the reference list of selected citing papers.
- Count the number of references of the citing papers which were published in 2013-15 irrespective of the journal (whether it is in “ABC” or in any other).
- To calculate citation potential, take average of reference list papers published in 2013-15.
- SNIP=2016 Impact Factor/2016 Citation Potential
SNIP value helps to compare journals on quality basis not on the citation behaviour.
Reference: Moed, H.F. (2010). Measuring contextual citation impact of scientific journals. Journal of Informetrics, 4(3), 265–277.
Source : https://www.elsevier.com/editors-update/story/journal-metrics/
Impact per Publication (IPP)
A journal’s Impact per publication (IPP) is calculated for the articles, review and conference papers published in a journal. Let’s consider the year 2016 for which we want to calculate the IPP.
IPP= Number of citations in 2016 to the articles published in the years 2013-15 / Total number of articles published in the years 2013-15 in the same journal
CiteScore
CiteScore is introduced in Dec 2016 to cover all journals indexed in Scopus and somewhat similar to Impact per publication with a small modification:
CiteScore= Number of citations in 2016 to the articles published in the years 2013-15 / Total number of articles indexed in Scopus published in the years 2013-15 in the same journal
The difference between IPP and CiteScore is the coverage of the document type. IPP metric calculation considers article, review and conference papers whereas CiteScore considers documents beyond it such as books, editorial and conference proceeding etc.
Source : CiteScore: a new metric to help you track journal performance and make decisions by Hans Zijlstra and Rachel McCullough, December 2016
Difference between impact factor and IPP
- IPP calculation is based on Scopus bibliography database vs. impact factor (IF) is based on Web of Science.
- IPP considers three years database vs. IF works for two years publications
- IPP is calculated considering scientific field difference vs. IF consider no field difference
- IPP calculation is limited to article, review and conference papers vs. IF calculation considers all document types such as books, editorial and conference proceeding etc.
So far, we have discussed a number of performance metrics in order to gain an insight into the journal performance. A researcher has multiple options (in terms of metrics) to calculate the journal performance while searching for an appropriate publication venue.
Note: Please read about Journal Performance Metrics (Part-A) here.