Danny Finkelstein makes an obvious, if oft-ignored or forgotten, point and does so with his customary elegance:
This idea of [Arthur] Laffer's is clearly true. We don't know what the curve (does it have a different dips for different taxes or a sharp fall near 100 per cent, say) would look like exactly and we don't know the lags. But obviously something like a Laffer curve must exist.
But the reverse Laffer argument is also true. If tax rates were 0 per cent there would be no tax revenue. So there must come a point at which as you cut taxes revenue falls.
The relationship between tax rates and revenue is therefore not as simple as Maurice [Saatchi] argues. Lower tax rates do not necessarily mean higher tax revenues.
Someone should probably mention this to the Republican party.