1. Department of Economics, Columbia University, 1022 International Affairs Building, MC 3308, 420 West 118th Street, New York, NY 10027 (e-mail: )
2. Department of Economics, University of California–Santa Cruz (UC Santa Cruz), Engineering II, Santa Cruz, CA 95064 (e-mail: )
3. Department of Economics, University of California–Davis (UC Davis), One Shields Avenue, Davis, CA 95616 (e-mail: )
4. Stephen M. Ross School of Business, University of Michigan, 701 Tappan Street, R5396, Ann Arbor, MI 48109 (e-mail: )