1. Department of Management Science, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan
2. Department of Finance and Economics, Rutgers University, Rockafeller Road, Piscataway, New Jersey 08854-8054, USA
3. Graduate Institute of Finance, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan