[1] Iowa State Univ, Dept Econ, Ames, IA 50011 USA
[2] Univ Chicago, NBER Res Associate, Booth Sch Business, Chicago, IL 60637 USA
[3] Michigan State Univ, Dept Econ, Dept Agr Food & Resource Econ, E Lansing, MI 48824 USA
[4] Michigan State Univ, Environm Sci & Policy Program, E Lansing, MI 48824 USA