1. Graduate Student, Montpellier Research in Economics (MRE) and Labex Entreprendre; University of Montpellier; 34960, Montpellier France
2. Telecom ParisTech; 75013, Paris France
3. Orange France; 75015, Paris France
4. Professor, Telecom ParisTech; 75013, Paris France
5. School of Economics; University of Cape Town; 7701, Cape Town South Africa
6. Professor, Department of Economics; University of Vienna; 1090, Vienna Austria
7. WIFO, 1030, Vienna, Austria; CEPR; London EC1V 0DX, UK