1. Harvard Business School, Boston, Massachusetts 02163;
2. National Bureau of Economic Research, Cambridge, Massachusetts 02138;
3. Université Paris Dauphine-PSL, 75016 Paris, France;
4. Télécom Paris, Institut Polytechnique de Paris, 91120 Palaiseau, France;
5. Center for Economic Studies and Ifo Institute for Economic Research, 81679 Munich, Germany