[1] Univ Patras, Dept Management Sci & Technol, Megalou Aleksandrou 1, Patras 26334, Greece
[2] Univ Pretoria, Dept Econ, ZA-0002 Pretoria, South Africa
[3] Helmut Schmidt Univ, Dept Econ, Holstenhofweg 85,POB 700822, D-22008 Hamburg, Germany
[4] Pusan Natl Univ, Dept Econ, 2 Busandaehak Ro 63beon Gil, Busan 46241, South Korea