The vast majority of immigrants in the United States have been admitted legally, although nearly 50 percent of people polled on this question believe most immigrants are here illegally. The United States has more immigrants than in the past. Immigration in the 1980s and 1990s is higher than it was from 1930 to 1979, but one-third what it was in the late 19th and early 20th centuries. The remainder of undocumented immigrants enter legally on student or tourist visas and then stay on after those visas expire. Most Mexican nationals residing in the United States at any given time are migrants, not immigrants.
Migrants are workers who take seasonal jobs and return to their families in Mexico.
Immigrants are people who intend to make their permanent home in this country. Although many people believe millions of undocumented Mexicans live in the United States, in reality the number is between 250,000 and 300,000 in any given year. Immigrants take jobs away from U.S. native-born workers. Immigrants generally create job opportunities for others. When the local impact is negative, it is very small.