The purpose of this paper is to extend the earlier analysis of the
sources and direction of agricultural productivity growth over time and
of agricultural productivity differences among countries which Yujiro
Hayami and Vernon W. Ruttan presented in their book on Agricultural
Development: An International Perspect.:ve.' In the Hayami-Ruttan
study the induced innovation hypothesis was tested against the historical
experience of agricultural productivity growth in Japan and the United
States for the period 1880—1960. In this paper it has been possible to
include four additional countries—Denmark, France, Germany, and the
United Kingdom—in the analysis and to extend the analysis for all six
countries to 1970. In the Hayami-Ruttan study the analysis of the
sources of productivity differences among countries was based on cross
section data centered on 1960. In this paper it has also been possible
to analyze the sources of productivity differences among countries using
data centered on 1970, and to compare the results with the earlier
analysis.