CWTS Journal Indicators currently provides four indicators:
In the calculation of the above indicators, only publications that are classified as article, conference paper, or review in Scopus are considered. Publications of other document types are ignored. Citations originating from such publications are ignored as well. Furthermore, citations are not counted if they originate from special types of sources (referred to as non-citing sources), in particular trade journals and sources with very few references to other sources (which includes many sources in the arts and humanities). For more details on the distinction between citing and non-citing sources, please see Section 4 of our paper.
IPP and SNIP are provided with stability intervals. A stability interval reflects the stability or reliability of an indicator. The wider the stability interval of an indicator, the less reliable the indicator. If for a particular source IPP and SNIP have a wide stability interval, the indicators have a low reliability for this source. This for instance means that the indicators are likely to fluctuate quite significantly over time. CWTS Journal Indicators employs 95% stability intervals constructed using a statistical technique known as bootstrapping.
The main differences between the indicators provided by CWTS Journal Indicators, in particular the IPP and SNIP indicators, and the journal impact factor (JIF) can be summarized as follows:
In the interpretation of the indicators provided by CWTS Journal Indicators, in particular the IPP and SNIP indicators, please take into account the following considerations:
All statistics provided by CWTS Journal Indicators can be downloaded in an Excel file. For each combination of a source and a year, the Excel file provides the corresponding indicator values and, in the case of IPP and SNIP, the stability intervals. In addition, the Excel file indicates whether a source is a citing source or a non-citing source. As explained above, citations originating from non-citing sources are not counted in the calculation of IPP and SNIP.