"The history of immigration to the United States has been shaped both by changes in the underlying costs and benefits of migration as well as by substantial shifts in immigration policy. The high cost of crossing the Atlantic in the seventeenth and eighteenth centuries gave rise to a long period of indentured immigration (c. 1600-1800). With revolutions in shipping technology and a growing reliance on a network of migrant finance, migration costs declined in the mid-nineteenth century, ushering in a sustained Age of Mass Migration from Europe (1850-1920). This period ended with the imposition of a literacy test for entry in 1917 and strict immigration quotas in 1921, which were modified (although not eliminated) in 1965. Most recently, the relaxation of immigration quotas has allowed for a period of constrained mass migration, primarily from Asia and Latin America. The rise of mass migration was associated with the shift from sail to steam technology in the mid-nineteenth century, and a corresponding decline in the time of trans-Atlantic passage. As travel costs fell and migrant networks expanded from 1800 to 1850, the number of unencumbered immigrants entering the US increased substantially. Annual in-migration rose from less than one per 1,000 residents in 1820 to 15 per 1,000 residents by 1850. Throughout the Age of Mass Migration (1850-1920), about 55 million immigrants left Europe, with the US absorbing nearly 30 million of these arrivals (Hatton and Williamson, 1998, p. 7). As a result, the foreign-born share of the population rose from 10 percent in 1850 to 14 percent in 1870, where it remained until 1920."