This entry in the data turns out to be a pretty good proxy for carried interest, as the fund manager of an investment fund is typically itself organized as a partnership. (By contrast, it is not unusual for the general partner of a real estate partnership to be an individual.)

The I.R.S. data is broken down by industry. In 2012, finance partnerships earned just over one trillion in income, about half of which ($527 billion) was taxed at long-term capital gains rates or preferential dividend rates. Within this group, “partnership general partners” reported $78 billion in income. The same group reported $53 billion in 2011 and $56 billion in 2010. About $40 billion, or half of the $78 billion, was taxed at low rates; applying a 20 percent rate increase would raise $8 billion a year.

One could argue, I suppose, that 2012 was not a representative year. But recent years have been even better. For example, Kohlberg Kravis Roberts alone earned about $8 billion in carried interest in 2014. The Blackstone Group reported earning $4 billion in carried interest.

My starting point for carried interest — the data on “partnership general partners” — is underinclusive. Individuals and corporations organized under Subchapter S also receive carried interest. And then one must add back in other industries, like real estate, that also generate carried interest.

If you add the amount of carried interest earned by general partners, there is about $200 billion annually in carried interest income, of which about $100 billion is taxed at low rates. Applying a 20 percent tax rate increase yields $20 billion a year, or $200 billion over 10 years. Applying a 10 percent haircut for factors like the actual invested capital of managers and anticipated changes in behavior, and the bottom line is $180 billion over 10 years.

The vast difference between the government’s estimate and my own is attributable to the anticipated behavioral response to the tax change, which one can think of as dynamic scoring on a microeconomics level.

For example, imagine that we doubled the capital gains rate to 40 percent from 20 percent. We would not get twice as much revenue as we do now. Some owners of appreciated property would feel “locked in” and defer the sale of assets.