Econometric studies of the effects of research on productivity have typically imposed arbitrary restrictions on the length and shape of the R&D on productivity and the estimated rate of return to research. This paper argues that the useful stock of public knowledge depreciates, if at all, only...

Transgenic crops are relatively new technologies being adopted rapidly in the United States and in a few other countries. The economic impacts of these technologies have, thus far, been estimated in a piecemeal fashion. The purpose of this study was to collect and characterize the economic...