WILLIAM J. SEROW is Associate Director of the Center for the Study of Population and Professor of Economics at Florida State University. He is the author of many articles and books on topics relating to migration, small area demography, population economics, and the demographic and economic aspects of aging.DAVID F. SLY is Director of the Center for the Study of Population and Professor of Sociology at Florida State Universtiy. He is the author of many articles and books on topics relating to migration, urbanization, human ecology, and the demographic and social aspects of aging.J. MICHAEL WRIGLEY has been a Postdoctoral Fellow at the Center for Demographic Studies at Duke University since 1988. He is the author of several articles on health and mortality, migration, and human ecology.