"Between 1800 and 1860, the United States became the preeminent world supplier of cotton as output increased sixty-fold. Technological changes, including the introduction of improved cotton varieties, contributed significantly to this growth. Measured output per worker in the cotton sector rose four-fold and large regional differences emerged. By 1840, output per worker in the New South was twice that in the Old South. The economy-wide increase is explained, in equal measure, by growth in output per worker at fixed locations and by the reallocation of labor across regions. These results offer a new view on the dynamics of economic development in antebellum America"--National Bureau of Economic Research web site.