1. Institute of Economics, Scuola Superiore Sant’Anna, Piazza Martiri della Libertà, 33, 56127 Pisa, Italy
2. Paris School of Economics, Université Paris 1 Panthéon-Sorbonne, CES, 106-112 bd de l'Hôpital, 75013 Paris, France
3. OECD Directorate for Science, Technology and Innovation 2, Rue André Pascal, 75016 Paris, France
4. Centre for Economic Performance (CEP), London School of Economics and Political Science, Houghton St, London WC2A 2AE, UK
5. SERC, London School of Economics and Political Science, Houghton St, London WC2A 2AE, UK