1. Department of Economics, University of Pennsylvania, 3718 Locust Walk, Philadelphia, PA 19104 (e-mail: )
2. Research Department, Federal Reserve Bank of Philadelphia, Ten Independence Mall, Philadelphia, PA 19106 (e-mail: )
3. Department of Economics, University of Bonn, Institute for Macroeconomics and Econometrics, Adenauerallee 24-42, 53113 Bonn, Germany (e-mail: )
4. Department of Economics, Emory University, Rich Memorial Building, Room 306, Atlanta, GA 30322; Federal Reserve Bank of Atlanta; and BBVA Research (e-mail: )