[1] Univ Salerno, Dept Econ & Stat, Via Giovanni Paolo II,132, I-84084 Fisciano, SA, Italy
[2] Univ Salerno, Ctr Econ Lavoro & Polit Econom CELPE, Fisciano, Italy
[3] Inst Univ Lisboa ISCTE IUL, Business Res Unit BRU IUL, Ave Forcas Armadas, P-1649026 Lisbon, Portugal
[4] TU Wien, Inst Stat & Math Methods Econ, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria