1. University of Chicago, 1155 East 60th St., Chicago, IL 60637 and NBER.
2. School of Education, University of California, Irvine, 2056 Education Building, Irvine, CA 92697.
3. Institute of Human Development and Social Change, New York University, 246 Greene St., Floor 6E, New York, NY 10003 and NBER.
4. Department of Economics, Harvard University, Cambridge, MA 02138 and NBER.
5. Department of Health Care Policy, Harvard Medical School, 180 Longwood Ave., Boston, MA 02115.
6. Congressional Budget Office, 2nd and D Streets, SW, Washington, DC 20515, and NBER.
7. NBER, 1050 Massachusetts Ave., Cambridge, MA, 02138.