In this paper, Mitsuo Saito and Ryoichi Nishimiya present a quantitative evaluation of the contributions of various factors to Japanese economic growth over the period 1962-73. The method adopted involves simulations using a macroeconometric model. which combines the Keynesian theory of effective demand with elements of neoclassical growth theory to describe both short-term fluctuations and long-term tendencies of the economy. The advantages of this new method over the traditional approach are discussed. According to Saito and Nishimiya's estimates, the contribution of technical progress to Japanese economic growth is larger than that suggested by the traditional method of growth accounting.