Efficient timing of income taxes

The marginal collection cost of an income tax is predicted to be a martingale, and the marginal income tax rate is predicted to be a supermartingale. Collection costs can be estimated from tax rates. Almost all tests based on a U.S. series of actual marginal income tax rates, 1913–1975, accept the hypothesis of random-walk behavior in collection costs, and reject the parallel hypothesis on tax rates.