The civil rights movement of the 1960s led to the replacement of these ethnic quotas with per-country limits. Since then, the number of first-generation immigrants living in the United States has quadrupled, from 9.6 million in 1970 to about 38 million in 2007. Nearly 14 million immigrants entered the United States from 2000 to 2010. and over one million persons were naturalized as U.S. citizens in 2008. Since the per-country limit applies the same maximum on the number of visas to all countries regardless of their population, it has had the effect of severely restricting the legal immigration of persons born in Mexico, India, China, and the Philippines – currently the leading countries of origin of immigrants to the United States.
Family reunification accounts for approximately two-thirds of legal immigration to the US every year. As of 2009, 66% of legal immigrants were admitted on this basis, along with 13% admitted for their employment skills and 17% for humanitarian reasons.