1. Stanford University, Stanford, California 94305; and National Bureau of Economic Research, Cambridge, Massachusetts 02138
2. Harvard Business School, Boston, Massachusetts 02163; and National Bureau of Economic Research, Cambridge, Massachusetts 02138
3. Copenhagen Business School, 2000 Frederiksberg, Denmark; Columbia Business School, New York, New York 10027; and Centre for Economic Policy Research, London EC1V 0DX, United Kingdom
4. Stockholm School of Economics, SE-113 83 Stockholm, Sweden; Institute for Financial Research, SE-111 60 Stockholm, Sweden; and Centre for Economic Policy Research, London EC1V 0DX, United Kingdom