The Laffer Curve argues the proposition that changes in the rates by themselves can affect govt revenues. This is different from other tax arguments, e.g., reduced rates increase demand because people have more after-tax dollars to spend.
Fern
I agree with the proposition, but disagree that it's different from other tax arguments. Yes, it's talking about changes in the rates themselves affecting revenues. But the reason the curve isn't linear is due to the assumption (and at least at the extremes the correct one IMO) that changes in the tax rate will affect the economy and therefore the tax base. From your link:
The "economic effect" assumes that the tax rate will have an impact on the tax base itself. At the extreme of a 100% tax rate, the government theoretically collects zero revenue because taxpayers change their behavior in response to the tax rate: either they have no incentive to work or they find a way to avoid paying taxes. Thus, the "economic effect" of a 100% tax rate is to decrease the tax base to zero.
Reduced rates increasing demand sounds like an an 'economic effect' to me.
Personally, I agree with the principle in general, but disagree on the curve's shape. I imagine it's much more like a linear graph with a slightly negative second derivative, but then precipitously drops at very high rates.