Author: Yoshimi Okada (Hitotsubashi University)
In order to assess the disclosure function of the patent system, this study examined the impact of the pre-grant publication system introduced in the United States in 2000. Unlike earlier studies, the applicant (inventor) non-self-citations (excluding examiner citations) were used to track knowledge flow. The causal effects of disclosure were identified by examining the changes in behavior before and after this legal change. The introduction of the pre-grant publication system was found to accelerate the initiation of knowledge diffusion significantly across all technology areas, except for Chemical field. The effect was the strongest in the Computers & Communications field, which had the longest publication lag before the reform. In addition, the initial slope of the diffusion curve rose while the long-term level of citation flow declined in the Computers & Communications field. In contrast, both of them rose in the Electrical & Electronic field. These results suggest the possibility that early disclosure not only stimulated complementary inventions but also helped inventors recognize early the duplications and then helped the reductions of duplicative R&D and/or applications, in a field with a long publication lag. In addition, we found that the examiner citation curve begins significantly earlier and more sharply compared to the applicant citation curve, which shows that examiner citation is a wrong measure of knowledge flow.