Everyone on the right loves to point to the Laffer curve to justify tax cuts, but fundamentally all it says is that tax revenue is zero if tax rates are zero and zero if tax rates are 100% and that there's a peak somewhere in the middle that maximizes the tax revenue. Where that peak is probably varies depending on the rest of the economy, but my understanding is that nobody who actually looks at this stuff rigorously actually thinks we're on the high taxation side of the peak. Maximizing revenue obviously isn't the only goal in setting tax policy, but we've done this experiment several times now and it holds up each time.