1. Fisher Business School, The Ohio State University, Columbus, Ohio 43210;
2. National Bureau of Economic Research, Boston, Massachusetts 02138;
3. Università della Svizzera Italiana, 6900 Lugano, Switzerland;
4. Swiss Finance Institute, CH-1211 Geneva 4, Switzerland;
5. Villanova School of Business, Villanova University, Villanova, Pennsylvania 19085;
6. Wharton Research Data Services, Philadelphia, Pennsylvania 19104