Humberto Llavador Universitat Pompeu Fabra   Department of Economics Universitat Pompeu Fabra R. Trias Fargas, 25-27 Barcelona, 08005 Spain   Humberto.llavador@gmail.com   http://www.econ.upf.edu/~llavador           JEL Areas: D7 : Analysis of Collective Decision-Making: General D6 : Welfare Economics: General