Senior Fellow, Resources for the Future, 2000 - present.
Distinguished Professor of Economics (Visiting), Oberlin College, 2000 - 2001.
Senior Economic Counselor to the Under Secretary for Global Affairs, U.S. Department of State, 1999 - 2000.
Professor of Public Policy and Management (Visiting), University of Pennsylvania, Wharton School, 1999.
Visiting Scholar, Resources for the Future, 1995 - 1999.
Gottesman Distinguished Professor of Economics (Visiting), Yeshiva University, 1996 - 1997.
Professor of Economics (Adjunct), American University, 1994 - 1996.
Deputy Administrator (Acting), U.S. Environmental Protection Agency (EPA), 1993.
Assistant Administrator for Policy, Planning and Evaluation (Acting), U.S.
Environmental Protection Agency (EPA), 1991 - 1993.
Director, U.S. Environmental Protection Agency (EPA), Office of Policy Analysis, 1982 - 1995.
Director, The Urban Institute, Energy Program, 1980 - 1982.
Legislative Assistant to Senator J. Bennett Johnston, 1979 - 1980.
Deputy Assistant Administrator for Energy, Natural Resources, and the Environment, Congressional Budget Office, 1976 - 1979.
Associate Professor, City University of New York, Queens College, Department of Economics (with tenure), 1971 - 1976.
Assistant Professor/Instructor, American University, Department of Economics, 1969 - 1970.