The approach of tax-filing day on April 15 invariably lowers spirits in the United States. Many taxpayers expect a refund when they have finished their calculations, but even this does little to improve the mood. The system’s surreal complexity is enough to defeat candidates for senior positions in the Treasury, let alone Joe the Plumber. Struggling with it arouses the suspicion that the income tax code is chiefly an instrument of political repression – a reminder of who is in charge.

Ceaseless meddling by Congress has encrusted the tax with extraordinary complications. The code tries to encourage or discourage most things, often both at once. The dozens of tax shelters for savings, for example, overlap in bewildering ways. Nobody seems to understand how the various reliefs interact – least of all the professional tax preparers who handle most of the work – so their incentive effect is, shall we say, muted. All a saver can be sure of is that if he comes to be audited, he will be in trouble.