1. Ph.D. Candidate, Pardee RAND Graduate School, RAND Corporation, 1776 Main St., Santa Monica, CA 90407.
2. Professor, Pardee RAND Graduate School; and Senior Engineer, RAND Corporation, 4570 Fifth Ave., Pittsburgh, PA 15213 (corresponding author).
3. Professor, Pardee RAND Graduate School; and Physical Scientist, RAND Corporation, 4570 Fifth Ave., Pittsburgh, PA 15213.
4. Professor, Pardee RAND Graduate School; and Economist, RAND Corporation, 1200 South Hayes St., Arlington, VA 22202.