Endogenous Fertility and the Design of Family Taxation

The paper innovates on the existing optimal taxation literature by taking fertility as endogenous, and allowing for households to be differentiated by their ability to raise children, as well as by their ability to raise income. In a context where the government cannot observe personal abilities, fertility behaviour conveys a great deal of information about those characteristics, which helps to relax the self-selection constraints on re-distribution. Bi-dimentional household differentiation introduces the possibility that re-distribution will be from households with low utility to households with high utility, and that it may be optimal to accentuate or reverse the sign of laissez-faire utility inequality. Contrary to popular belief, we find that it is not necessarily optimal for the tax system to be so designed that an additional child would lighten the tax burden on his or her parents. If it is, the optimal policy may include an unusual mix of taxes on number of children, subsidies on child-specific commodities, income support for low-wage households, and positive marginal income tax rates for all.