Comparison of IPC and USPC classification systems in patent prior art searches

Patent classification systems are used to help scrutinize patent applications for possible violations of the novelty and non-obviousness/inventive steps of a patentability test. There are several different patent classification systems in use today, each with a different underlying philosophy and approach. We compare the two most widely-used patent classification systems -- the IPC and USPC -- and examine their ability to help re-rank patents based on similarity. We observed a significant improvement in MAP, Recall@100, and nDCG when using these systems to re-rank our retrieved document set, demonstrating their overall utility in patent searches.