Chain migration for the U.S. refers to the pattern of family members following a previous immigrant to the U.S., or a foreigner who arrives by virtue of marriage to an American.
According to the Center for Immigration Studies, in chain migration, spouses and children of citizens accounted for about 30% of permanent immigrants who came in 2015. Parents of citizens account for about 12% of all immigrants that year. Adding all family related categories, half of the 1,052,000 immigrants in 2015 were family related. There is no formal way of classifying these family-related immigrants by whether they work and if so what they do. Only 144,000 immigrants in 2015 were awarded green cards on the basis of work,
For every admitted family related immigrant, there are close to nine such individuals on the waiting list. As of November 2016, there were 4.3 million people who had been sponsored by a relative in the United States who were on the waiting list for family-based immigrant visas. They face waiting periods of 22 months to 23 years, depending on the category and the country of origin. Over half of these applicants were siblings of American citizens.
The CIS cites studies that estimate in recent years each new immigrant sponsored an average of 3.45 additional immigrants. In the early 1980s, the chain migration multiplier was 2.59, or more than 30 percent lower. Mexico has the highest rate of chain migration. In the most recent five-year cohort of immigrants studied (1996-2000), each new Mexican immigrant sponsored 6.38 additional legal immigrants.