A patent only protects an innovator from others producing the same product, but it does not protect him from others producing better products under new patents. Therefore, one may divide up the source of competition facing an innovator into within-patent competition, which results from...

Coe and Helpman(1995) have measured the extent to which technology spills over between industrialized countries through the particular channel of trade flows. This paper re-examines two particular features of their study. First, we suggest that their functional form of how foreign R&D affects...