1. Dipartimento di Scienze Teoriche e Applicate, Università degli Studi dell’Insubria, 21100 Varese, Italy
2. Department of Economics and Statistics, University of Siena, 53100 Siena, Italy
3. Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Lungotevere Thaon di Revel 76, 00196 Rome, Italy