Let’s pretend we have a modest tax rate of 20 percent. Now imagine you are part of an industry with $200 million in profits and you want a special tax break. How much are you willing to pay to get that loophole?

Well, with a 20 percent tax, the most you can save (assuming the loophole is huge and you wipe out all your tax liability) is $40 million.

So how much would you spend on lobbyists, campaign contributions, etc, in order to get that loophole? That’s hard to answer, because it would require some estimate of the probability of success. But one thing we can safely assume is that the industry would never spend more than $40 million.

But let’s now assume you live in a world with 50 percent tax rates. Does that change the incentive for influence peddling in Washington? Of course it does. The industry’s tax bill is now $100 million, so it now has an incentive to spend up to that amount to get special treatment.