From a  WSJ editorial on how higher marginal tax rates in the U.K. lowered tax revenues from Britain’s top earners, confirming that the Laffer curve is real and that “if you tax something, you actually do get less of it”:

“Speaking of higher taxes (and President Obama always does), there’s news from once fair Britannia. Preliminary figures out this week show that Britain’s 50% top marginal income-tax rate may have reduced tax revenue from top earners by as much as 5%, compared to the old 40% top rate. Tax revenue from those filing self-assessments due January 31 was down some £500 million versus last year. 

What this week’s numbers teach, however, is that Britain’s richest taxpayers are simply shifting their incomes, or themselves, offshore, or deferring income, or otherwise arranging their affairs to avoid the confiscatory new top tax rate. Maybe that’s unfair, too—the rich are usually better at protecting their assets—but it’s the predictable consequence of a tax rate whose animating purposes are envy and spite.”