So why would you want to put this as part of a tax package? And perhaps the number one reason is that it could raise a lot of revenue. And depending on how high this tax is, you'll raise more rather than less. But an estimate's very, but something like $33 per ton of CO2 in 2020 could raise about $180 billion per year. And so the revenue estimate trajectories start out at around $100 billion when the taxes impose, it kind of rates I was talking about. As the tax ramps up, the revenue doesn't necessarily increase all that fast because people are responding precisely in the way you want them to by emitting less and using less of those fuels. So the revenue kind of goes up a ways and then eventually it tapers off as the rate goes up and the emissions fall faster than the rate goes up. And eventually this tax somewhere out in the latter part of this century would end up and not very much revenue at all. So this would be an intermediate medium to long run revenue instrument. But eventually in the very long run it would not be a revenue instrument at all. And that's what you need if you're going to stabilize concentrations. You need those emissions to taper off. So aside from the revenue, you want the carbon tax embedded in a tax, bigger tax package because it's regressive. And if you don't embed it in a broader tax reform, you either fix the regressivity as part of the carbon tax proposal or you don't fix it at all. And so if you try to fix the regressivity within the carbon program, what you end up doing is something like maybe rebating some of the tax to households to blunt their energy bills. Well, what's that going to do? It's going to blunt the insun of to conserve energy. And there you have to have a higher carbon tax to reach the same environmental objective. And that obviously makes it more costly. Third, if you use carbon tax revenue for deficit reduction, you might obviate some of the rents seeking that plagued the discussion of cap and trade. I mean, in the cap and trade debates, relatively little of the squabble was over the cap. It was who got the allowances. All that activity meant that anybody who thought they were about to lose their share of the piece of pie had the incentive to block the whole measure. So they could get another bite at the pie. So if all that revenue goes to deficit reduction or embedded tax reform, then there's nothing to squabble over. And me, you can actually get something done. Finally I think that if you don't use the revenue for tax reduction, you're going to get a lot more costly climate program. This is a robust result on a lot of the climate policy literature. If you have a climate program that just takes the allowances and gives them away or takes a revenue and gives it away, you're not offsetting those other distortionary taxes and you're not getting that economic benefit. And that raises the overall cost of the climate program considerably.