[1] Univ Bologna, Dept Agr Econ & Engn, I-40127 Bologna, Italy
[2] European Commiss, Joint Res Ctr, Inst Prospect Technol Studies, Seville 41092, Spain
[3] Louisiana State Univ AgCtr, Baton Rouge, LA 70803 USA
[4] Louisiana State Univ, Dept Agr Econ & Agribusiness, Baton Rouge, LA 70803 USA
[5] Univ Bologna, Dept Stat Paolo Fortunati, I-40126 Bologna, Italy