Little more than four decades separated the Franco-Prussian War of 1870–1871 from the first World War of 1914–1918. In terms of material welfare, upon which the economists helped to fix attention, these were the most successful decades in history. In 1650 there were apparently something like half a billion inhabitants of this planet. During the forty-five years from 1870 to 1914 nearly half a billion were added. Population increased by almost as large a number in a generation and a half as it had increased during untold generations separating Adam from Newton. In the wealthier countries of Western Europe (Great Britain, Sweden, Norway, Germany and France) and in North America, the real income per person gainfully employed has been estimated to have improved seventy-five percent or more, while the hours of work were substantially reduced. In the United States the per capita output of the manufacturing industries grew nearly four times over. Professor Tawney has explained that, “during the greater part of history, the normal condition of the world has been one of scarcity. … But, as a result of the modernization of production and transport, first in Great Britain, then on the continent of Europe and in North America, then in parts of the Far East, mere scarcity ceased, after the middle of the nineteenth century, to be, except in the last, the haunting terror which till recently it had been.”