The tax cut isn't a gift. It is a decrease in the amount of money the federal government is confiscating from the citizenry.
So it's not about "proving" it worked, it's about proving it did harm. And I can tell you that the Bush tax cut did some good - if allowed us to hire one additional person who in turn was assigned to help create this website.
Col Gene: I don't like deficits either. But I don't like them as a matter of principle.
Can you name a single negative real world side effect of the deficit? Because the theory of deficits is that they will raise interest rates because the government is competing with private investors to get loans. But the interest rate is also at a near all time low as well.
I worry more about the spending on welfare than the interest on the debt: