Income taxation of couples and the tax unit choice

We study the optimal income taxation of couples. We determine the
resulting intra-family labor supply allocation and its implication for the choice
of the tax unit (individual versus joint taxation). We provide a general condition
for full joint taxation to arise. We also study how the spouses’ respective
labor supply decisions are distorted when the condition does not hold. In
particular, we show that, depending on the pattern of mating, the celebrated
result according to which the spouse with the more elastic labor supply faces
the lower marginal tax rates may or may not hold in our setting.