1. University of Copenhagen, Øster Farimagsgade 5, Bld. 26, 1353 Copenhagen, Denmark, and CEPR (email: )
2. University of Warwick, Scarman Rd, CV4 7AL Coventry, United Kingdom, and CEPR (email: )
3. University of Copenhagen, Øster Farimagsgade 5, Bld. 26, 1353 Copenhagen, Denmark (e-mail: )
4. University of Copenhagen, Øster Farimagsgade 5, Bld. 26, 1353 Copenhagen, Denmark (email: )