The UK’s new 50% tax rate for incomes over £150k has reduced tax revenues.
The amazing thing is that anyone is surprised by this. The existence of a Laffer curve is unarguable (one cannot contest the simple observation that the government will receive no revenue at a tax rate of 0% or 100%), the only dispute is where the curve peaks. All the evidence shows that curve peaks much lower than 50%.
Of course, there are those who support counterproductive tax rates even knowing they are counterproductive, out of sheer spite.
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