Patent citation indicators: One size fits all?

The number of citations that a patent receives is considered an important indicator of the quality and impact of the patent. However, a variety of methods and data sources can be used to calculate this measure. This paper evaluates similarities between citation indicators that differ in terms of (a) the patent office where the focal patent application is filed; (b) whether citations from offices other than that of the application office are considered; and (c) whether the presence of patent families is taken into account. We analyze the correlations between these different indicators and the overlap between patents identified as highly cited by the various measures. Our findings reveal that the citation indicators obtained differ substantially. Favoring one way of calculating a citation indicator over another has non-trivial consequences and, hence, should be given explicit consideration. Correcting for patent families, especially when using a broader definition (INPADOC), provides the most uniform results.