Comparing the IPC and the US classification systems for the patent searcher

Abstract

This paper provides a detailed comparison of the two major patent classification systems in use, the International Patent Classification (IPC) and the United States Patent Classification (USC). A data set of over 400 `family' records, where each `family' comprises the equivalent US and EP granted patents, is created for this analysis. A first comparison is made between the IPC as applied by the USPTO and the IPC as applied by the EPO. A second comparison is then made between the USC applied and the IPC as applied by the EPO. The comparisons highlight the significantly different approaches of the two systems, primarily in the relative weighting that is given to the inherent functionality of each invention and to its application in a specific industry. Examples are provided where this difference has led to a plurality of IPC terms corresponding to a single USC term, and vice versa. Similar situations arise with the IPC as applied by the USPTO, using a concordance between the USPC and the IPC; some 18% of these IPC terms differ from the EPO-applied IPC at the highest (section) level. The implications of the findings for patent searchers are explored.