Keynes' general attitude toward mathematical economics and econometrics, respectively, is discussed in Sections 2-3. The remainder of the paper is devoted to a description and analysis of the interaction between the Keynesian revolution of the mid-1930's and the revolution that had actually started somewhat earlier with respect to the preparation of current official estimates of national income. In this connection an attempt is made to explain why Kuznets' work in the U.S. in the early 1930's was immediately integrated into official national income estimates in the U.S., where Colin Clark's work in Britain was not--with the result that official British national income estimates did not begin to appear until almost a decade later.