“I think the massive boom in Mexican immigration is over and I don’t think it will ever return to the numbers we saw in the 1990s and 2000s,” said Douglas Massey, a professor of sociology and public affairs at Princeton University and co-director of the Mexican Migration Project, which has been gathering data on the subject for 30 years. Nearly 1.4 million Mexicans moved from the United States to Mexico between 2005 and 2010,