First Author:   Seonghoon Jeon Sogang University jeonsh@ccs.sogang.ac.kr   Department of Economics, Sogang University, C.P.O. Box 1142 Seoul, 121-742, Korea   +82 2 705 8517(Phone) +82 2 705 8517(Fax) http://www.sogang.ac.kr/~jeonsh