[1] Univ Aquila, Dept Ind & Informat Engn & Econ, Laquila, Italy
[2] Univ Minho, Dept Econ, Campus Gualtar, P-4710057 Braga, Portugal
[3] Univ Minho, Ctr Res Econ & Management NIPE, Campus Gualtar, P-4710057 Braga, Portugal
[4] London Sch Econ & Polit Sci, LSE Alumni Assoc, Houghton St, London WC2 2AE, England