[1] Oregon State Univ, Dept Econ, Corvallis, OR 97331 USA
[2] Hong Kong Baptist Univ, Dept Econ, Kowloon Tong, Hong Kong, Peoples R China
[3] Univ Queensland, Sch Econ, St Lucia, Qld 4072, Australia
[4] Univ Queensland, Ctr Efficiency & Prod Anal, St Lucia, Qld 4072, Australia