1. Columbia Business School and National Bureau of Economic Research (NBER), 623 Uris Hall, 3022 Broadway, New York, NY 10027 (e-mail: )
2. (e-mail: )
3. U.S. Department of Veterans Affairs Health Economics Resource Center and Stanford University School of Medicine, Health Economics Resource Center, Veterans Affairs Medical Center, 795 Willow Road, Menlo Park, CA 94025 (e-mail: )
4. Columbia University School of Nursing, 617 W. 168th St., Room 228, New York, NY 10032 (e-mail: )