1. Department of Economics, University of Chicago, 1126 E. 59th St., Chicago, IL 60637, University College Dublin, and American Bar Foundation.
2. Department of Economics, University of Chicago, 1126 E. 59th St., Chicago, IL 60637.
3. Department of Economics, Vanderbilt University, PMB 351819, 2301 Vanderbilt Place, Nashville, TN 37235-1819, and Robert Wood Johnson Center for Health Policy, Meharry Medical College.