When choosing among money managers, investors pay attention to pretax performance, which is disclosed, and not after-tax performance, which is not usually disclosed as clearly, if at all. A crucial reason for this is that different investors have different tax profiles, and so it is difficult for an asset manager to disclose performance in terms of a single after-tax rate of return. As a result, most asset managers don’t pay close attention to investor-level taxes.

Many investors are tax-exempt.

Mrs. Clinton wants to focus on “cut and run” investors out to make a quick buck. Some private equity funds would seem to fit that description. A fund manager who buys a company, sells assets, fires workers and sells the company for a gain two years later would seem to be affected by Mrs. Clinton’s proposal.

The problem is that the fund manager is investing other people’s money.

Private equity funds raise money from institutional investors like pension plans, university endowments, foundations and insurance companies. A majority of these investors are tax-exempt. As a result, those investors are indifferent to the capital gains rate.

Carried interest is calculated on a pretax basis.

Still, not all investors are tax-exempt. Wouldn’t taxable investors in private equity encourage fund managers to change their behavior in response to rising capital gains taxes?

Perhaps, but fund managers are not likely to listen. A major element of the fund manager’s compensation, known as carried interest, is the percentage of profits, typically 20 percent, allocated to the fund manager in exchange for managing the fund and its portfolio companies. Profits are calculated without taking investor-level taxes into account.

Hit and run is not the usual strategy.

An increase in the capital gains rate could affect the fund manager personally, but not as much as you would think. The holding period of investments is determined at the fund level, and the average holding period for private equity is about five years. Under Mrs. Clinton’s plan, the rate on such investments would be just 4 percent higher than current law.

Managers of activist hedge funds don’t change behavior in response to capital gains rate changes.

Consider activist hedge funds, another target for Mrs. Clinton. Again, although the fund manager might be personally affected by capital gains rates, most of the investors are tax-exempt, and the fund manager’s carried interest is based on pretax, not after-tax, returns. Fund managers are unlikely to hold an investment for a longer period if it jeopardizes their carry, and it’s not clear that we would want them to.