Verdissement de la fiscalité : à qui profite le double dividende ?

The double dividend literature studies the simultaneous pursuit of two objectives - improving the quality of the environment through the introduction or enhancement of an environmental tax (first dividend) and increased social welfare by reducing distortions induced by the whole the tax system (second dividend). By investigating the conditions that would reconcile the double dividend with some social equity criteria, this work goes beyond the usual results of the literature in which the second dividend is to be achieved at the expense of a group of agents who should bear the main part of the tax burden. The reform should achieve three goals: environmental quality, economic efficiency (ie the macroeconomic gains) and the Pareto improvement. These objectives therefore require three instruments: the environmental tax, the income tax and the index of tax progressivity. We show that the redistributive properties of the income tax could be a tool for correcting social distortions induced by the environmental policy. We propose to recycle the revenues of the carbon tax by a nonlinear decrease of the income tax among households, combining a decrease in the tax rate of the first bracket of income tax (which benefits all agents) with a higher rate for the upper brackets (which cost will be mainly supported by highest classes of income). This latter mechanism could compensate the regressive characteristics of the carbon tax.