Applicant Prior Art Disclosure and Examination Performance: Evidence from Japan

The identification of relevant prior art is a key step in assessing an invention's contribution; however, it remains unclear whether and how applicants can contribute to this process through prior art disclosure. This study investigates how applicant disclosures causally affect patent examination performance using the Japanese Patent Office's 2002 policy reform requiring applicant disclosure as a natural experiment. We find that this reform has significantly improved the quality of applicant disclosure (as measured by its coverage of examiner citations of prior art), especially for high-quality inventions. The reform led to faster grant processing, a narrower initial patent scope, and fewer amendments between applications and grants, primarily through higher-quality disclosure. While the reform also led to a greater number of disclosures not used by examiners, which had the effect of slowing the grant process, this effect was dominated by the effect of higher quality. The reform also increased the total amount of prior art used by examiners and reduced both invalidation and rejection appeal trials through higher disclosure quality. Applicant disclosures complemented examiner search efforts, thereby enhancing the overall prior art base used in patent examinations.