"The process by which the US economy was mobilized during World War I was the subject of considerable criticism both at the time and since. Nevertheless, when viewed in the aggregate the degree of mobilization achieved during the short period of active US involvement was remarkable. The United States entered the war in 1917 having made only limited preparations. In 1918 the armed forces were expanded to include 2.9 million sailors, soldiers, and marines; 6 percent of the labor force in the 15 to 44 age bracket. Overall in 1918, one fifth or more of the nation's resources was devoted to the war effort. By the time the Armistice was signed in 1919 a profusion of new weapons was flowing from American factories. This essay describes how mobilization was achieved so quickly, including how it was financed, and some of the long-term consequences"--National Bureau of Economic Research web site.