China's "great migration": the impact of the reduction in trade policy uncertainty / Giovanni Facchini (University of Nottingham, University of Milan, CEPR, CESifo, CReAM, GEP, IZA and LdA), Maggie Y. Liu (Smith College), Anna Maria Mayda (Georgetown University, CEPR, IZA and LdA), Minghai Zhou (University of Nottingham, Ningbo China) ; IZA Institute of Labor Economics. Bonn, Germany : IZA Institute of Labor Economics, January 2018