Comparison of US, EPO, and PCT Patent Citations for Citation Analysis

Patent citation analysis in the United States has traditionally used the citations on U.S. patents as the data source. Recently, however, it has been suggested that referencing practices in the European Patent Office (EPO) and the Patent Cooperation Treaty (PCT) may make citations on those documents more useful as indicators. This paper summarizes the results of a statistical comparison of citations on patent documents from the U.S. Patent & Trademark Office (USPTO), the EPO, and the PCT to determine whether more information could be extracted from EPO and/or PCT citations than from using U.S. citations alone.