One of the more interesting documents published by the IRS — I know, I know, not the hardest criterion in the world — is its report on the income and taxes of the top 400 taxpayers (pdf). A lot of attention gets focused, rightly, on the remarkably low average tax rate these people pay — less than 17 percent in 2007, the lowest on record.

But I was struck by something else: in several years during the last decade the top 400 accounted for more than 10 percent of all capital gains income in America. Just 400 people!

Conservatives often try to sell the notion that reducing the capital gains tax is about helping small business people. But you really want to think of the fact that a significant chunk of that tax break is going to just 400 people.

And when you think about financial regulation, you similarly want to bear in mind that when asset prices rise, a tiny handful of people get a large chunk of the gains; I don’t know this for sure, but I’d bet that they somehow end up bearing a much smaller share of the losses when the bubble bursts.

Anyway, think about it: a lot of policy is dictated by the interests of a group of people who, if you could separate them from their entourages, would fit easily into McCosh 10.