1. Department of Economics Boston University, 270 Bay State Road, Boston, MA 02215, and NBER (e-mail: )
2. Department of Economics and International Business School, Brandeis University, 415 South Street, Waltham, MA 02454 (e-mail: )
3. Division of Research and Statistics, Federal Reserve Board, 20th Street and Constitution Avenue NW, Washington, DC 20551 (e-mail: )
4. Division of Monetary Affairs, Federal Reserve Board, 20th Street and Constitution Avenue NW, Washington, DC 20551 (e-mail: )