1. Department of Economics; University of Southern California; Los Angeles CA 90089 USA
2. Department of Economics; Yonsei University; Seoul Korea
3. Universite de Montreal; CIREQ; CIRANO; C.P. 6128, Succ. centre-ville Montreal QC H3C 3J7 Canada
4. Cowles Foundation; Yale University; PO Box 208281 New Haven CT 06520-8281 USA
5. Department of Economics; University of Auckland; Owen G. Glenn Building, Private Bag 92019 Auckland 1142 New Zealand