The VAT has taken the tax world by storm over the last fifty years, but left little trace in the academic literature. Bird and Gendron provide an impressively informed and informative account of the VAT experience in lower income countries, largely vindicating the tax and standard advice for its design. But they rightly stress too that dominant “expert opinion” on the VAT remains troublingly uninformed by serious analysis and evidence. This article focuses on some of these gaps and recent attempts to start filling them.

This paper analyzes Pareto-efficient international tax regimes. Because every country faces its own national budget constraint, the Diamond-Mirrlees production-efficiency theorem, which underlies key tenets of policy advice in international taxation—the desirability of destination basis for commodity taxation, of the residence principle for capital income taxation, and of free trade—does not apply. The paper establishes conditions—relating to the availability of explicit or implicit devices for reallocating tax revenues across countries—under which production efficiency is nevertheless desirable, and characterizes the precise ways in which Pareto-efficient international taxation may require violation of established tenets.

Closer international integration is putting increasing pressure on existing national tax structures. This paper uses a simple two-country model to address a range of consequent policy concerns, focusing particularly on the role of country size. Differences in size exacerbate the inefficiency from noncooperative behavior, harming both countries. The smaller country loses from harmonization to any tax rate between those set in the noncooperative equilibrium, but both countries gain from the imposition of a minimum tax anywhere in that range. The fully optimal response to freer cross-border trade, however, may be to do nothing.

The relative strengths of vertical and horizontal tax externalities turn on the balance between the interest responsiveness of the supply of savings and demand for capital, the extent to which immobile factors are taxed by the states, and the strength of preferences between federal and state expenditures. The vertical externality will dominate if the aggregate tax base of the federation is responsible to the state tax instrument. Tax interactions in federations are more complex than has often been supposed.