[1
]Department of Psychology, University of British Columbia, 2136 West Mall, Vancouver,
Canada V6T 1Z4
[2
]Department of Economics, University of British Columbia, 2136 West Mall, Vancouver,
Canada V6T 1Z4
[3
]Centre for Health Evaluation and Outcome Sciences, Providence Health Care Research
Institute, University of British Columbia, Vancouver, British Columbia, Canada V6Z
1Y6