"In the middle decades of the 19th century, new immigrants were the ready source of labor to unload ships, to build roads and canals, and to transport goods (Carter 2006: I-590-591). With the growth of factories and the demand for unskilled labor, immigrants, primarily young men in the working years, continued to be the ideal source of labor. Immigrants were generally more willing to accept lower wages and inferior working conditions than native born workers (Zolberg 2006: 69). Great efficiencies in production led to higher profits that could be reinvested in new technology, which led to even more production and eventually higher wages for workers. Although the demand for manufactured goods gradually grew to encompass the entire country, the initial demand was from the urban population. Unlike farm families that were largely self sufficient in food and made most of their clothing, urban families needed to purchase everything in the market. The large and growing urban populations, primarily fueled by immigration throughout the second half of the 19th century and the first two decades of the 20th century, created a huge demand for the increased production of the emerging industrial sector. Carter and Sutch (1999: 330–331) claim that economies of scale in demand and production also stimulated inventive activity and the diffusion of technological knowledge and innovation. In his analysis of long swings, or Kuznets cycles, Easterlin (1968) found that immigration (and population growth) and subsequent family formation stimulated economic growth through increasing demand for housing, urban development, and other amenities. This association was strongest, Easterlin noted, in the century prior to World War II. In the post World War II era, the federal government assumed more responsibility for maintaining aggregate demand regardless of population dynamics."