Patent citation indicators: one size fits all?

The amount of citations that a patent receives is considered as an important indicator of the quality and impact of the patent. However, different methods and data sources are used to calculate this measure. This paper evaluates the similarities between citation indicators obtained when counting within different patent offices (USPTO, EPO and patent applications filed through the PCT). Additionally we discuss the effects of using indicators that correct for patent family and the effects of including citations from more than one source. Our findings reveal that the obtained citation indicators differ substantially. This is confirmed when comparing sets of highly cited patents identified by these different indicators. Correcting for patent families remedies this situation, at least if a broad definition (INPADOC) of families is being adopted. Our findings suggest that favoring one way of calculating a citation indicator over another, has non-trivial consequences and hence should be considered explicitly. If...