You're right -- the effect is, of course, indirect. Cutting taxes stimulates economic growth; economic growth increases government revenues. That increase may or may not cover the difference between what is collected and what would have been collected.

I'd also agree that the gov't is short of revenues, but that's determined by two factors: revenue and spending levels.

Congress acts on the AMT a year at a time, because a permanent fix changes the projected revenues and the corresponding projected deficit over multiple years.

I appreciate the idea of incenting people to buy fuel-efficient vehicles, but current fuel prices have put us (taxpayers) in the odd position of subsidizing the purchase of vehicles that would be produced at max capacity and sold within days, even without a tax credit.