Bocar Samba Ba Université Clermont Auvergne, CNRS, CERDI, F-63000 Clermont-Ferrand, France   29, rue de la Liève Clermont-Ferrand, Auvergne 63100 France   bocar_samba.ba@uca.fr             JEL Areas: Q5 : Environmental Economics: General H2 : Taxation, Subsidies, and Revenue: General