1. University of Verona, Via Cantarane 24, Verona, Italy
2. Mines ParisTech, 60 Boulevard Saint-Michel, Paris and ZEW Centre for European Economic Research, Mannheim, Germany
3. Schmalkalden University of Applied Science and ZEW Centre for European Economic Research, Mannheim, Germany
4. University of Warwick, Coventry CV4 7AL