1. Research Institute for Economics and Business Administration, Kobe University , 2-1 Rokkodai, Nada, Kobe, Hyogo 657-8501 , Japan
2. Faculty of Policy Management, Keio University , Endo 5322, Fujisawa, Kanagawa 252 - 0882 , Japan
3. Saïd Business School, University of Oxford , Park End Street, Oxford OX1 1HP , UK