Induced Innovation in United States Field Crops, 1939‐78

During the past four decades, United States field crop production has been transformed by the mechanical and fertiliser revolutions. In this study crop‐specific estimates of the technical progress parameters that represent these changes are used to test the microeconomic theory of induced innovation. Tests based on the land/labour ratio, derived from a reformulation of the Hayami and Ruttan model, entirely support the inducement hypothesis and suggest that the partial failure of previous empirical investigations resulted from specification problems.