Paul R. Portney is president and a senior fellow of Resources for the Future. He is the author, editor, or coeditor of several books, including Discounting and Intergenerational Equity and Footing the Bill for Superfund Cleanups: Who Pays and How?Robert N. Stavins is the Albert Pratt Professor of Business and Government and faculty chair of the Environment and Natural Resources Program at the John F. Kennedy School of Government at Harvard University. He is also chair of the Environmental Economics Advisory Committee of the EPA's Science Advisory Board. His recent publications include Economics and the Environment: Selected Readings.