Contribution of Patent Examination to Making the Patent Scope Consistent with the Invention: Evidence from Japan

Delineating the patent scope consistently with the contribution of the disclosed invention is one of the most crucial requirements for a patent system to promote innovation effectively. Given the incentive of an applicant to set a scope for the patent as broad as possible, an important task of the Patent Office is to narrow it so that it becomes commensurate with the invention. This study analyzes empirically how significantly the Patent Office delivers this important function through patent examination, focusing on product patents in four major technology areas. We find that, often (i.e., two-thirds of the granted patents), the patent's scope is narrowed as an outcome of the patent examination. In addition, both the incidence and the extent of such narrowing increase when the applicant chooses broader claims and decrease when the quality of prior art disclosure by the applicant is higher, suggesting that patent examination indeed contributes to making the patent scope consistent with the contribution of the invention. We also found that a more important patent application experiences more the narrowing event, consistent with our simple model of examination where an examiner aims at reducing the economic cost due to excess claim such as deadweight loss, subject to time constraint.