1. Department of Economics; Stern School of Business; New York University; 44 West 4; th; Street, New York; New York; 10012; U.S.A.
2. Centro Estudios Monetarios y Financieros (CEMFI); Casado del Alisal 5; Madrid; Spain
3. London School of Economics; Houghton Street; London; WC2A 2AE; England