He claims it's closer to 45 or 50 percent:
John Berlau and Trey Kovacs of the WSJ make the same argument:
One reason investment income is taxed at a lower rate than wage and salary income is because it is a double tax—profits are taxed once under the statutory 35% corporate tax rate and then again when they are paid out to individuals as dividends.
Daniel Shaviro counters:
Berlau and Kovacs are entirely right to suggest that the corporate level tax matters to the analysis. I frequently noted this point in the carried interest debate a couple of years back. But they are of course wrong (in classic WSJ fashion) to simply assume that corporations are actually paying tax on 35% of their income.
Jared Bernstein sides with Shaviro:
Based on Romney’s tax returns, it’s impossible to tell whether the capital gains he realized through these companies reflect corporate taxes at all (interestingly, Romney’s trustee actually made this point to the WSJ, which chose to ignore it).
Finally, remember this: [private equity firms (PEs)] are masters of debt financing, and debt financing carries an effective tax rate of -6% because business interest can be deducted from your tax bill. For the highly leveraged PE crowd, debt financing is a tax shelter for other liabilities they face, including any corporate income that might slip through the cracks…if I were the WSJ here, I’d crow that Romney’s tax rate is actually 9% (15-6)!
The Dish 