Coe and Helpman (1995) and others report positive and equivalent R&D spillovers across G7 countries. We argue that their homogeneity constraint on spillovers across G7 countries is inappropriate, and show that it is rejected by the data. Extending the data set and applying new empirical...

Coe and Helpman (1995) among others report positive and equivalent R&D spillovers across groups of countries. However, the nature of their econometric tests does not address the heterogeneity of knowledge diffusion across countries. We empirically examine these issues in a sample of 10 OECD...