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.