The tax on the wealthy is only on income. Many of the wealthiest don't have income so they come under a different classification that is not called income. They get a lower tax. This is one scam that is backed by the Whitehouse. Senator Kerry gets taxed on a Senator salary but has assets with his wife that are in the hundreds of millions.
Another scam are deductions, which were not addressed. Romney was smart since he was going to lower the tax rate, since the tax rate is more for show when it comes to the most wealthy. He was going reduce deductions where the money magic really occurs. This is what allows the rich and well connected get to lower their final tax rate. General Electric had the sanme corporate rate as large business, but through deductions did not have to pay taxes.
Polititians don't like to touch deductions, because this is how they money launder campaign donations from wealthy special interest groups. The tax code is a who's who of campaign money laundering.
If you were to touch deductions, the tax code would shrink shrink and the kickback scam would be harder. For example, unions contributed to Obama, so they get a deduction/exemption from Obamacare. They get their contribution money back by donating up front. If we eliminated all new deductions, then campaign contributions may not be cost effective. Hollywood got a new deduction since they provided campaign value via propaganda. They are very wealthy and may say we accept higher rates, but will pay less.
Romney was well aware of how the game works. But since the game is still on, he and the other smart rich will always win the game, since there is always a need for money laundering by polititians.