Demographers explore population diversity in the United States.

Nancy A. Denton is Associate Professor of Sociology at the University at Albany, State University of New York. She is the coauthor, with Douglas S. Massey, of American Apartheid: Segregation and the Making of the Underclass. Stewart E. Tolnay is Professor of Sociology at the University of Washington. He is the author of The Bottom Rung: African American Family Life on Southern Farms.