Household-level panel data from a nationally representative sample of rural Indian households describing the adoption and profitability of high-yielding seed varieties (HYVs) associated with the Green Revolution are used to test the implications of a model incorporating learning by doing and learning spillovers. The estimates indicate that imperfect knowledge about the management of the new seeds was a significant barrier to adoption; this barrier diminished as farmer experience with the new technologies increased; own experience and neighbors' experience with HYVs significantly increased HYV profitability; and farmers do not fully incorporate the village returns to learning in making adoption decisions.
This paper argues that the 'scale effects' prediction of many recent R&D-based models of growth is inconsistent with the time-series evidence from industrialized economies. A modified version of the Romer model that is consistent with this evidence is proposed, but the extended model alters a key implication usually found in endogenous growth theory. Although growth in the extended model is generated endogenously through R&D, the long-run growth rate depends only on parameters that are usually taken to be exogenous, including the rate of population growth.