A la recherche d'une fiscalité optimale des revenus

This article surveys the economic theory that designs the optimal nonlinear income tax schedule that trades off the equity gains of a more progressive income tax schedule against the incentives to work less induced by such a more progressive income tax schedule. We take into account not only the effects of the income tax schedule on the incentives for employed workers to work harder (the incentive margin) but also the incentives on the decision to work or not (the extensive margin). We first expose a heuristic derivation of the optimal tax formula to clarify the economic intuitions behinds it. We then explain how to retrieve this formula in a rigorous way using optimal control tools.