The importance of international technology diffusion (ITD) for economic development can hardly be overstated. Both the acquisition of technology and its diffusion foster productivity growth. Developing countries have long sought to use both national policies and international agreements to stimulate ITD. The 'correct' policy intervention, if any, depends critically upon the channels through which technology diffuses internationally and the quantitative effects of the various diffusion processes on efficiency and productivity growth. Neither is well understood. New technologies may be embodied...