Under Herman Cain's 9-9-9 tax reform plan, 84% of U.S. households would pay more than they do under current tax policies

And the impact would be felt most heavily by the lowest income groups. Those are some of the estimates from the Tax Policy Center's analysis of Cain's proposal, which has helped make him a leading contender for the Republican 2012 presidential nomination. While some key questions about the 9-9-9 plan remain unanswered, the Tax Policy Center's analysis is one of the first to take a comprehensive look at its potential impact. Cain's 9-9-9 plan would replace much of the current tax code with a flat-rate system: a 9% individual income tax; a 9% corporate income tax and a 9% national sales tax. Estate and gift taxes would be eliminated, as would the payroll tax, and most tax credits, deductions and exemptions. In terms of investment taxes, capital gains would be tax-free, while dividends would be deductible to businesses paying them out but taxable at 9% for investors who receive them. According to the Tax Policy Center, households with incomes below $30,000 would have, on average, between 16% and 20% less in after-tax income than they do today. By contrast, households making more than $200,000 would see their after-tax income grow by between 5% and 22% on average.