Yair Listokin (Yale) recently presented Taxation and Marriage: A Reappraisal at Columbia and Harvard:

An income tax cannot simultaneously maintain progressive marginal tax rates, an equal tax burden for all married couples with identical incomes (“couples equity”), and neutrality with respect to the tax burden of married vs. unmarried couples (“marriage neutrality”). Existing treatment of this “trilemma” of taxation and marriage typically argue that marriage neutrality is a more important principle than couples equity ot vice versa. The literature therefore advocates wholesale abandonment of either marriage neutrality or couples equity. The literature also treats progressive taxation as outside the scope of the problem of marriage taxation. In this paper, I argue (in both prose and in a formal model) that the prior literature is flawed. The costs of violating the principles of couples equity and marriage neutrality are not linear — large violations of either principle are considerably worse than small violations of both. Instead of solving the trilemma by strict adherence to couples equity and deliberate disregard of marriage neutrality (or vice versa), the taxation of marriage should violate both principles to a lesser degree, sharing the burden of the trilemma more broadly. The trilemma’s burden can also be dissipated by a reduction in progressivity, thus bringing progression back into the discussion of taxation and marriage.