1. Department of Economics, Seinan Gakuin University, Fukuoka 814-8511, Japan
2. Department of Management Information, Kyoto College of Economics, Kyoto 610-1195, Japan
3. Faculty of Social Relations, Kyoto Bunkyo University, Kyoto 611-0041, Japan
4. Center for Infectious Disease Education and Research, Osaka University, Osaka 565-0871, Japan