violence and civil unrest in Central America during the 1980s, immigrant Salvadorans, Guatemalans, and Nicaraguans tripled their numbers in the United States in the 1990s. The number of foreign-born Dominicans, Peruvians, and Bolivians doubled in the 1980s, and then doubled again in the 1990s. New migrant streams such as these generally portend increased momentum of immigration because once established, immigrant social networks provide a powerful impetus for future flows. These circumstances also contribute to the growth of undocumented immigration.
A distinctive feature of Hispanic immigration is the large and growing number of undocumented immigrants. The best contemporary estimate is that close to 11 million undocumented migrants resided in the United States in 2005, 80 percent of them from Mexico and other Latin American countries.14 Mexicans alone account for 57 percent of the entire undocumented population, and more than 80 percent of all Mexican immigrants who arrived in the United States after 1990 were undocumented.15 For perspective, the number of undocumented residents in the United States is larger than the populations of some Latin American countries, such as Uruguay, Paraguay, Nicaragua, El Salvador, or Costa Rica.
Many decades in the making, undocumented Hispanic immigration is in part a consequence of both employer demand for cheap, hardworking laborers and failed immigration policy (see Table 2-1).16 Primarily at the behest of American growers, immigration laws in 1921 and 1924 that were designed to exclude immigrants from Asia, Africa, and nonwestern Europe explicitly exempted persons from Mexico, Cuba, Haiti, the Dominican Republic, the Canal Zone, and the independent countries of Central and South America from the numerical quotas.17 This conveniently permitted unregulated recruitment of Mexican workers as needed and their prompt deportation when they were not, as occurred during the 1930s when about 400,000 (including, as it happened, many U.S. citizens) were repatriated to Mexico. During the mid-1950s, Operation Wetback resulted in the repatriation of even larger numbers of Mexicans—again, legal residents and U.S. citizens among them.18
Several other factors have contributed to the intense flow of undocumented immigration from Mexico. First, the termination in 1964 of the Bracero Accords, which authorized a binational agricultural guestworker program, signaled the closing of an important labor safety valve precisely at