ABSTRACT
The first part of the analysis of economic growth consists, then, in deriving concepts of economic growth and in devising means of measuring it or, at least, of establishing criteria by which to judge whether there was, at any given period, growth or contraction. Historians and economists seem to know well enough what they mean by economic growth or contraction. The second part of the analysis of observed growth is the study of the factors that economists and historians have adduced in explanation. The third task in the analysis of economic growth is called as 'describing mechanism'. In the Smith-Mill-Marshall theory, the economy grows like a tree. When trying to form an opinion about the effects on economic growth in the United States of a reduction of the income tax in the higher brackets we have to distinguish two things: the effect upon investment and the effect upon motivation.
