[1] Univ British Columbia, Dept Econ, Vancouver, BC V6T 1Z1, Canada
[2] NBER, Vancouver, BC V6T 1Z1, Canada
[3] Univ Toronto, Dept Econ, Toronto, ON M5S 3G7, Canada
[4] Univ Toronto, Rotman Sch Management, Toronto, ON M5S 3G7, Canada
[5] NBER, Toronto, ON M5S 3G7, Canada