Nancy L. Green is a professor of history at the École des Hautes Études en Sciences Sociales. She is a coeditor of Citizenship and Those Who Leave: The Politics of Emigration and Expatriation and author of The Other Americans in Paris: Businessmen, Countesses, Wayward Youth, 1880-1941 . Roger Waldinger is Distinguished Professor of Sociology at UCLA. He is editor of Strangers at the Gates: New Immigrants in Urban America and author of The Cross-Border Connection: Immigrants, Emigrants, and Their Homelands .