We thank Olivier Blanchard, Henning Bohn, David Romer, and participants at the IMF's Eleventh Annual Jacques Polak Research Conference for helpful comments and suggestions. Any errors are the authors' responsibility. The views expressed herein are those of the authors, and should not be attributed to the IMF, its Executive Board, its management, or the National Bureau of Economic Research. NBER working papers are circulated for discussion and comment purposes. They have not been peerreviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications.