1. Economics Department, Columbia University, 420 West 118th Street, New York, USA. E‐mail: jb3064@columbia.edu
2. CEMA, Central University of Finance and Economics, Beijing, China.
3. AQR‐IREA Research Group, Department of Econometrics, Statistics and Spanish Economy, University of Barcelona, Av. Diagonal, 690, 08034 Barcelona, Spain. E‐mail: carrion@ub.edu