Amid all the talk this election season about tightening security along the U.S.-Mexico border, legions of Mexican immigrants have been exiting the U.S. because of the economic crisis. For instance, municipal officials in Mexico City predict that 20,000 to 30,000 of the city's former residents will move back this Christmas alone. That may be due in part to rising unemployment among Mexican immigrants, which, according to the Pew Hispanic Center, is now higher than the jobless rate for the general workforce in the U.S. Mexicans also sent home 12% less cash in August than they did in the same month last year, the biggest decline in over a decade. All of which is bad news for Mexico, since remittances are its second-largest source of foreign income after oil exports.