[1] Natl Univ Singapore, Dept Econ, 21 Lower Kent Ridge Rd, Singapore 119077, Singapore
[2] Univ Pretoria, Dept Speech Pathol & Audiol, Lynnwood Rd & Roper St, ZA-0001 Pretoria, South Africa
[3] Univ Western Australia, Ear Sci Ctr, Sch Surg, 35 Stirling Hwy, Perth, WA 6009, Australia
[4] Ear Sci Inst Australia, 2-1 Salvado Rd, Subiaco, WA 6008, Australia
[5] Natl Univ Singapore, Saw Swee Hock Sch Publ Hlth, 12 Sci Dr 2,10-01, Singapore 117549, Singapore
[6] Hlth Promot Bur, Dept Hlth, Manila 1003, Philippines
[7] Natl Univ Singapore, Saw Swee Hock Sch Publ Hlth, 21 Lower Kent Ridge Rd, Singapore 119077, Singapore