**Michael Keen **, former deputy director of fiscal affairs at the International Monetary Fund, is Ushioda Fellow at Tokyo College, University of Tokyo.Joel Slemrod is the David Bradford Distinguished University Professor and the Paul W. McCracken Professor of Business Economics and Public Policy at...

**Michael Keen **, former deputy director of fiscal affairs at the International Monetary Fund, is Ushioda Fellow at Tokyo College, University of Tokyo.Joel Slemrod is the David Bradford Distinguished University Professor and the Paul W. McCracken Professor of Business Economics and Public Policy at the University of Michigan. They have both received the National Tax Association's Holland Medal for their lifetime contributions, and both are former presidents of the International Institute of Public Finance.