Hi Alicia   Perhaps I can provide an explanation.   Although both the Journal Citation Reports and Web of Science are derived from our primary production database, each has separate processes for aggregation and unification.  Web of Science is optimized for linking cited references to source items, a precise, point-to-point connection.  The JCR aggregates citations at the journal level - using any and all variants of the journal’s title that occur in a citation, and independently of whether or not the citation has linked to a specific item in the journal.  Each product’s processes are based on the needs of the individual product and will apply unification and aggregation procedures that are intended to optimize the data for the resulting product. 

 
While this creates a much better product in each case, it makes it very difficult, even for an expert in both products’ algorithms, to generate JCR citation data from Web of Science searches. I can identify for you some of the most common pitfalls when Web of Science users attempt this kind of search:


Although Web of Science is continually updated, JCR is like a snapshot from a specific timepoint when the data were extracted for analysis.  The JCR extraction usually occurs in early March of the year subsequent to the JCR year, and it is at this precise date that the JCR citing dataset is permanently defined; therefore, any late arriving citing materials from the JCR year that were indexed for Web of Science after extraction had occurred would not contribute citations to the JCR, but these citations would still be reflected in Web of Science Citation Report. So, the citations that occurred after March should not be included in your final calculations.


Secondly, the JCR will use multiple variants of the journal title, not just the 20 character abbreviation presented in JCR proper.  We also include cited references that are not linked to a specific source item, but that are clearly citations to the journal of record. This explains why the citations in the JCR were higher than you originally accounted for.


In essence, you have calculated the denominator correctly, as you can confirm from your own calculations, but the numerator is reliant on several other factors that cannot be accounted for when working in Web of Science only.


I hope I have answered your questions fully, but if there is anything else that needs to be addressed, please do not hesitate to let me know and I can connect you with our JCR editor.   Very best,  Lisa


Lisa Hulme 
Head of Global Communications - Web of Science Group
 

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