Unique journal impact metrics are used to measure the indicators of a rating of publications within the framework of scientometrics databases. For example, Web of Science uses the Impact Factor that we reviewed earlier. Today we will analyze the indicator Source Normalized Impact per Paper or abbreviated SNIP, which is used to evaluate journals in the Scopus database.
Calculation of the SNIP metric in Scopus
Information about SNIP indicators can be found on the source information page, near some metrics such as SJR and CiteScore.
Source Normalized impact per paper was developed in 2009 by Professor Hank Mohan of Leiden University (Netherlands). This organization is a partner of Elsevier. Therefore, the calculation of SNIP is carried out by scientists of the Center for Science and Technology Studies of Leiden University in partnership with specialists of Scopus, on the basis of materials that are indexed in this database.
The SNIP metric has been proposed as a universal citation metrics that can be used regardless of the log domain.
The indicators are measured by the ratio of the number of quotes to the number of articles in the last 3 years. The resulting indicator is then divided into normalized value of citing the subject area of the log. Only peer-reviewed papers, namely scientific articles, conference reports and Scopus reviews, are taken into account in calculating the metric.
CWTS Journal Indicators
The methodology proposed by Leiden University takes into account several unique identifiers. They are called CWTS Journal Indicators:
- P – the number of publications in the last three years.
- IPP – the indicator that takes into account the number of articles and quotations without taking into account the coefficient of the subject area. It is also worth noting that the publication window for the indicator is three years.
- SNIP – the normalized index that is computed using IPP and P, but with the inclusion of an integrated coefficient by subject domains.
- %self cit. – the level of self-citing of the journal, which is calculated in the percentage of all quotes of the journal to those where its own materials are quoted.
In addition to standardized IPP and SNIP indicators, minimum and maximum citation volumes (lower bound and upper bound) are calculated, but they are rarely used to assess the rating of the publication.
What does SNIP not account for?
The SNIP indicator is calculated mathematically, so you should pay attention to a number of its errors. This will help in the evaluation of journals and the selection of publications:
- Review articles. In scientometrics there is a certain pattern: review articles are cited more often than research articles. Therefore, the journals that target them have higher SNIP indicators.
- Self-citing. Although this indicator is calculated separately, some publications abuse it and actually slightly inflate their indicators.
- Small Publications. The developers of the methodology warn that CWTS Journal Indicators is representative only for publications with 50+ publications.
- Asymmetry of publications. Often there is a situation when in the publication most of the articles do not have a high level of citation. Only a few publications are referred to by a large number of scientists. Such highly cited works and improve the performance of the publication.
If you plan to publish your own article in the journals of Scopus or Web of Science databases, specialists of the company Scientific Publications will be glad to help you. We will analyze the work, issue it according to international standards, provide quality translation, check the level of uniqueness and correctness of citation. As a result, you will receive the publication and indexing of the research in the publication of the international scientific database Scopus or Web of Science. Contact us via chat or contact form on the site and our specialists will reply shortly.
Let’s remind you, the material has just come out «What are altmetrics and what resources are used for their analysis?»