1. Department of Statistics, University of Padova, Via Cesare Battisti 241, 35121 Padova, Italy, and IRVAPP.
2. Department of Economics, University of “Ca Foscari” of Venice, S. Giobbe 873 30121, Venezia, Italy, SSAV, and IFS.
3. Department of Economics, University of Padova, Via del Santo 33, 35121 Padova, Italy, CEPR and IFS.