CHARLES B. NAM is Professor of Sociology and Research Associate, Center for the Study of Population, Florida State University. His expertise is the result of almost 40 years in the field, including work with the U.S. Bureau of the Census in 1950 and 1960.WILLIAM J. SEROW is Professor of Economics and Associate Director of the Center for the Study of Population at Florida State University. He is the author of three previous books and numerous articles.DAVID F. SLY is Professor of Sociology and Director of the Center for the Study of Population, Florida State University. In addition to his work in the United States, he has lived and worked in Kenya, Holland, Belgium and Indonesia. He has written three previous books on population and migration.