1970-1970 Visiting Lecturer, University of Witwatersrand, Johannesburg, South Africa

1973-1973 Lecturer in Demography, University of California, Berkeley

1971-1973 Research Specialist and Head, Demographic Analysis Section, California State Department of Public Health, Berkeley

1973-1974 Actuary, U.S. Railroad Retirement Board, Chicago

1974-1976 Assistant Professor, Department of Sociology, University of Illinois at Urbana-Champaign

1976-1982 Associate Professor, Department of Sociology, University of Illinois at Urbana-Champaign

1982-1989 Professor, Department of Sociology, University of Illinois at Urbana-Champaign

1989-1999 Professor, Department of Population Dynamics, Johns Hopkins University, Baltimore

1999-Present Hoffman Professor of Family Sociology and Demography, Department of Sociology, Pennsylvania State University, University Park