Redistribution and taxation of labor income: an empirical study on French data.

Summary This thesis has a double objective: to inventory the concepts and results discovered by economists to analyze income distributions and direct taxation and to apply them to the study of the French fiscal and social system. In the first part, the measures of inequality are described and the use of the Lorenz criterion is justified with the work done since Atkinson. The relationship between progressivity and the equalizing power of tax scales is examined using Jakobson's approach, when incomes are exogenous. In France, incomes are successively subject to different levies, social contributions and income tax. Breton, Moyes and Trannoy studied the equalization properties of compound scales and established the necessary and sufficient conditions for inequality to be reduced when the degree of progressivity of an element of the compound scale is increased. The results are established independently of the distribution of primary incomes and focus on the function linking disposable income to primary income. In the second part, we present the theory of optimal taxation which asks how best to construct a tax system with redistributive objectives, defined by an exogenous social welfare function, when labor income is endogenous I. E. . Result from individual labor supply behavior. Incentive constraints limit government action: too much progressivity may undermine its objectives. In the third part, we describe the social and fiscal legislation and analyze the equalizing power of the French compound tax system from 1959 to 1996. We investigate whether it has reduced income inequality and study the evolution of the equalizing power of the compound tax scale, reasoning independently of the income distribution. This study also highlights the negative effects of certain mechanisms on equalization and efficiency.