1. Department of Economics and Statistics, University of Siena, Siena, Italy
2. Division of Social Sciences, New York University Abu Dhabi (NYUA), Abu Dhabi, United Arab Emirates and Centre for Economic Policy Research (CEPR), London, UK
3. Department of Economics and Statistics, University of Siena, Siena, Italy and Centre for Economic Policy Research (CEPR), London, UK, vasta@unisi.it