1. Department of Economics, Bowdoin College, 6000 College Station, 111 Hubbard Hall, Brunswick, ME 04011, USA
2. Independent Researcher, Bates College, 534 East Broadway, Boston, MA 02127, USA
3. Department of Economics, Bates College, 4 Andrews Road, 276 Pettengill Hall, Lewiston, ME 04240, USA
4. National School of Development, Peking University, Beijing 100871, China