From debates on Capitol Hill to the popular media, Mexican immigrants are the subject of widespread controversy. By 2003, their growing numbers accounted for 28.3 percent of all foreign-born inhabitants of the United States. This book analyzes the economic impact of this historically unprecedented exodus. Why do Mexican immigrants gain citizenship and employment at a slower rate than non-Mexicans? Does their migration to the U.S. adversely affect the working conditions of lower-skilled workers already residing there? And how rapid is the intergenerational mobility among Mexican immigrant families? This volume provides a historical context for Mexican immigration to the U.S. and reports new findings on an immigrant influx whose size and character will force us to rethink economic policy for decades to come.