Bonifacio Llamazares University of Valladolid, Spain   Dep. of Applied Economics Avda. Valle de Esgueva, 6 Valladolid, Valladolid 47011 Spain   boni@eco.uva.es   http://www2.eco.uva.es/boni/index_ing.htm           JEL Areas: H : Public Economics C0 : Mathematical and Quantitative Methods: General