1. Stanford Graduate School of Business, Stanford, California 94305
2. NHH Norwegian School of Economics, NO-5045 Bergen, Norway; and Research Institute of Industrial Economics (IFN), SE-102 15 Stockholm, Sweden
3. NHH Norwegian School of Economics, NO-5045 Bergen, Norway; and Stockholm School of Economics, SE-113 83 Stockholm, Sweden
4. Stockholm School of Economics, SE-113 83 Stockholm, Sweden
5. Cevian Capital, 114-32 Stockholm, Sweden