THEORY: National Income Between Wars

The most definitive study of the U.S. national income appeared last week.* It was an eight-year study by the No. 1 student of what the U.S. earns for itself, University of Pennsylvania's Simon Kuznets. Studded with tables, and with warnings about what Mr. Kuznets calls "the penumbra of conceptual and statistical vagueness," it is bound to become a dogeared source book for students of the U.S. economy. It also has some conclusions of interest to laymen about that economy's 20 between-war years (1919-38):

¶The proportion of U.S. income derived from agriculture, mining,...