via Reason: Taxpayers Aren't Stationary Targets.
Leaving recessions out of the account, for the past 60 years federal tax revenues have been rather steady at just under 19 percent GDP regardless of the tax rates. The top income-tax rate has ranged from a low of 28 percent in 1988-90 to a high of 92 percent in 1952-53, yet the flow of money has been a fairly constant proportion of the economy. This would seem to confirm the apparently controversial hypothesis that taxpayers are purposive human beings who can be counted to modify their behavior according to the incentives and disincentives that government places in their paths.
Yet most politicians don't get it. In The Wall Street Journal a few years ago, W. Kurt Hauser, formerly of the Hoover Institution, wrote:
Even amoebas learn by trial and error, but some economists and politicians do not. The Obama administration's budget projections claim that raising taxes on the top 2% of taxpayers, those individuals earning more than $200,000 and couples earning $250,000 or more, will increase revenues to the U.S. Treasury. The empirical evidence suggests otherwise. None of the personal income tax or capital gains tax increases enacted in the post-World War II period has raised the projected tax revenues.
"Hauser's Law" seems quite robust. Over 60 years, "there have been more than 30 major changes in the tax code including personal income tax rates, corporate tax rates, capital gains taxes, dividend taxes, investment tax credits, depreciation schedules, Social Security taxes, and the number of tax brackets among others. Yet during this period, federal government tax collections as a share of GDP have moved within a narrow band of just under 19% of GDP."
The explanation is simple enough for a child to understand, though politicians have difficulty with it:
When tax rates are raised, taxpayers are encouraged to shift, hide and underreport income. Taxpayers divert their effort from pro-growth productive investments to seeking tax shelters, tax havens and tax exempt investments. This behavior tends to dampen economic growth and job creation. Lower taxes increase the incentives to work, produce, save and invest, thereby encouraging capital formation and jobs. Taxpayers have less incentive to shelter and shift income.
Click the link to read the whole thing.