1. K. J. Arrow and R. G. Noll are in the Department of Economics, Stanford University, Stanford, CA 94305, USA.
2. M. L. Cropper is at the World Bank, 1818 H Street, NW, Washington, DC 20433, USA.
3. G. C. Eads is at Charles River Associates, 1001 Pennsylvania Avenue, NW, Washington, DC 20004, USA.
4. R. W. Hahn is at the American Enterprise Institute, 1150 17th Street, NW, Washington, DC 20036, USA.
5. L. B. Lave is in the Graduate School of Industrial Organization, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
6. P. R. Portney is at Resources for the Future, 1616 P Street, NW, Washington, DC 20036, USA.
7. M. Russell is in the Department of Economics, University of Tennessee, Knoxville, TN 37996, USA.
8. R. Schmalensee is at the Sloan School of Management, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
9. V. K. Smith is at Duke University, Durham, NC 27708, USA.
10. R. N. Stavins is at the John F. Kennedy School of Government, Harvard University, Cambridge, MA 02138, USA.