These groups represent 63.2% of the foreign-born older than five years, followed by Europeans (11.9%), Central Americans (11.2%), South Americans (7.3%), Asians (2.9%), and others (1.0%).
Political refugees have been a major source of flows to Mexico. The 1934-1940 administration of Lázaro Cárdenas welcomed 40,000 Republican exiles from the Spanish Civil War. Despite their small numbers, the descendents of these migrations and exiles from the 1970s 'dirty wars´ in the Southern Cone have had a disproportionately high impact on Mexican intellectual, cultural and professional life. In the 1980s, refugees from Central America began passing through Mexico in large numbers bound for the United States. About 80,000 Guatemalans sought refuge in Mexico from the Civil War. Many were housed in camps under the authority of the United Nations High Commissioner for Refugees. About three quarters returned to Guatemala following the 1996 peace accords, and the rest were given the option to naturalize in Mexico.
Mexico is a major country of transit for unauthorized migration to the United States. It shares more than 1000 kilometers of border with Guatemala and Belize, much of it through rugged jungle or forested terrain in the poorest parts of Mexico.
Train routes leading north have been a popular and dangerous means of illicit migration, all the more since gangs have made a steady business of preying on migrants. Since the 1990s, the Mexican authorities have increased their presence along transportation routes in the frontier region even as the border itself remains largely unguarded. Authorities denied entry or deported 125,000 migrants in 1990, which rose to 250,000 by 2005. The primary source countries of transmigrants are Guatemala, Honduras, and El Salvador. Despite these efforts, and given widespread corruption among Mexican law enforcement, many migrants are able to cross Mexico from south to north. In fiscal year 2005, non-Mexicans made up approximately 14 percent of U.S. Border Patrol apprehensions, most of them made on the U.S. Mexico border.