Patent Duration and Spillover of R&D

“Standing on shoulders” effects due to positive spillover externalizes are important to science and technology policies. We estimated spillover coefficient in the patent production functions across countries. We can find systematic relation between spillover and effective patent duration. For the latter issues, we considered patent renewal interval and grace period that is an exception for novelty requirement for patent registration. Overall, short duration leads to large spillover. And, this real duration also affects international spillover(knowledge transfer) between the US, Japan and Korea.