In all cases the authors benefited from the criticisms of the other contributors to this volume. In addition, the following members of the RFF administrative and research staff gave helpful suggestions and assistance: Daniel J. Basta, Emery N. Castle, James A. Embersit, Leonard Gianessi, Raymond Kopp, Herbert C. Morton, Talbot Page, Clifford S. Russell, and Glen Weinberg. The authors would also like to thank the following for helpful comments and discussion on earlier drafts: Edward Berger, J. Clarence Davies III, David Donniger, Herbert Kaufman, John Mendeloff, Robert Miki, William Schulze, Joseph Seneca, Jon Sonstelie, and William Sullivan. The computer programming assistance of Louanne Sawyer and the competent typing of Linda Perrotta and Diana Tasciotti are gratefully acknowledged. Chapter 5 is based largely on research conducted for the National Bureau of Economic Research by its author, and Leonard Gianessi, and Edward Wolff under National Science Foundation grant SOC 74-21391.