Herman Cain's "9-9-9" tax plan is an interesting and radical proposal. It would scrap the current federal tax code completely and replace it with a 9% income tax, a 9% national sales tax, and a 9% corporate tax. Since Cain continues to lead in the GOP polls, his plan clearly has some support at least among Republicans.
And it does make some major improvements on the current tax code. The payroll tax discourages hiring, hurts small businesses and low-income workers, and is almost hidden from view. The current marginal rates are very high, including a confiscatory 35% on businesses, which discourage production.Worst of all, the tax code is loaded with deductions and loopholes, which (combined with high marginal rates) encourage the special-interest lobbying and economic sleight-of-hand that are poisoning the current system. Under the current tax system it is very easy for the government to pick winners and losers. By zapping most of the deductions and loopholes and eliminating the payroll tax, Cain's plan does well.
The problem, though, is that the 9-9-9 plan is simply not fair.
There are three kinds of taxes. In a progressive tax, the rich pay a higher percentage than the poor. In a flat tax, everyone pays the same percentage. In a regressive tax, the poor pay a higher percentage than the rich.
Clearly, a regressive tax system would not be fair. We would also not want a tax system that is overly progressive. A very good argument can be made for a flat tax, as long as there exists a reasonable individual deduction to prevent the tax from hitting the very poor. There is also a very good argument for a tax system that is somewhat (but not overly) progressive. In the words of Adam Smith:
"It is not very unreasonable that the rich should contribute to the public expen[s]e, not only in proportion to their revenue, but something more than in that proportion."
Where does the 9-9-9 plan fall? Well, there are two taxes for individuals, the 9% income tax and the 9% sales tax. The income tax, of course, is flat. The problem is the sales tax. Sales taxes are almost always regressive, because the poor need to spend a higher percentage of the money they make. So the 9-9-9 plan replaces the current progressive tax system with a combination of a flat tax and a regressive tax, which is overall regressive.
That's not to say a national sales tax is a bad idea. While sales taxes are regressive, they do not distort incentives nearly as much as income taxes, because they discourage consumption instead of production. However, a national sales tax would need to be combined with a progressive income tax in order for the system to not be regressive overall. If Cain proposed a four-tier income tax (say, 5-10-15-20) with no loopholes or deductions, combined with a 9% national sales tax, a 9% corporate profits tax and a 9% capital gains tax, I'd vote for that in a second.