Illegal aliens are people who immigrate into a country without having proper documentation or approval by the country in question. Some aliens cross the border secretly; the majority arrive legally but overstay their visas.
- Employers like hiring non-Americans because they can pay illegal aliens less and ignore state and federal employment laws. Ann Coulter
Most experts estimate a total of about 12 million foreigners without legal status in the United States—although no one knows for sure. The Pew Hispanic Center in 2005 estimated that in 2004 13.9 million people lived in families in which the head is an unauthorized migrant. Of those individuals, some 3.2 million are US citizens by birth but are living in "mixed status" families in which a parent is unauthorized.
In general, illegal entry into the U.S. is a misdemeanor, not a felony. A large fraction of the illegals were brought in as children; babies born in the U.S. to illegal parents have full U.S. citizenship status.
In the United States, it is illegal and punishable by the law to hire a worker without legal work authorization. Employers who break this law can face stiff fines and /or imprisonment although most conservatives would argue that the law is very infrequently enforced.
Most of the recent debate focuses on Mexican border crossers who enter the country without legal documents. Undocumented immigration is estimated to have grown from about 3.2 million in 1986 to 12 million in 2007. Since the mid-1990s, annual arrivals of unauthorized migrants have exceeded those who come under legal categories.
Before 1910 the majority of illegals came from China, where they obtained false documents saying they were born in the U.S. (and therefore were citizens.) After 1910 Mexicans comprised over 90% of unauthorized population until the early 1970s. However by by 2002 they made up only about half of the illegals. The next largest groups come from Central America and South America (about 24 percent); smaller groups have arrived from Asia, Europe, and Africa.
- Pierre Hauser, Illegal Aliens (1990)
- Jeffrey S. Passel, "Unauthorized Migrants: Numbers and Characteristics," Pew Hispanic Center Reports and fact Sheets. (June 14, 2005), online
- Claudia Sadowski-Smith. "Unskilled Labor Migration and the Illegality Spiral: Chinese, European, and Mexican Indocumentados in the United States, 1882–2007," American Quarterly, Volume 60, Number 3, September 2008, pp. 779-804 in Project Muse
- Aristide R. Zolberg, A Nation by Design: Immigration Policy in the Fashioning of America (2006)
- See Passel (2005).