William G. Gale is Arjay and Frances Fearing Miller Chair in Federal Economic Policy in the Economic Studies Program at The Brookings Institution and Co-director of the Tax Policy Center. J. Mark Iwry is Non-resident Senior Fellow in the Economic Studies Program at Brookings, a Senior Staff Member at the Tax Policy Center, and the former Benefits Tax Counsel at the U.S. Treasury Department, where he initiated and directed Executive Branch approval and promotion of 401(k) automatic enrollment and automatic rollover. Alicia H. Munnell is director of the Center for Retirement Research at Boston College and the Peter F. Drucker Chair in Management Sciences at Boston College’s Carroll School of Management. Richard H. Thaler is the Robert P. Gwinn Professor of Behavioral Science, Economics and Finance at the University of Chicago’s Graduate School of Business. The authors thank Michael Henkel, John Kimpel, and David Wray for discussant remarks, Rep. Ben Cardin (D-MD) for his keynote address, and Brennan Kelly of The Brookings Institution for research assistance.