[1] Univ Salerno, Dept Econ & Stat, Salerno, Italy
[2] Univ Salerno, CELPE, Salerno, Italy
[3] Ruhr Univ Bochum, Chair Competit Theory & Policy, Bochum, Germany
[4] Univ Witten Herdecke, Dept Econ, Witten, Germany
[5] Univ York, HEDG, York YO10 5DD, N Yorkshire, England