From 9-9-9 to 9-0-9?

In response to criticism of 9-9-9's low-end regressivity, Herman Cain has apparently partially dropped one of the 9's. He is quoted by CNN as saying the following:

"If you are at or below the poverty level, your plan isn't 9-9-9 it is 9-0-9. Say amen y'all. 9-0-9."

This appears to refer to putting a zero bracket into the personal income tax (or wage tax?) portion of the 9-9-9 plan. However, three thoughts about this are the following:

(1) Poor people who are unemployed will get no benefit, since they already are earning zero. An 18 percent federal tax rate is a huge hike for them, compared to present law.

(2) Once you agree to a zero bracket, haven't you surrendered the entire supposed logic (whatever it is) of having a flat tax? This, of course, is also an issue for the so-called flat tax that Rick Perry is expected to endorse shortly. That proposal has historically had two brackets, one of them at zero percent, and I gather that the Perry proposal is expected to share this feature. So it isn't actually a flat tax.

Once you agree to a zero bracket, in a certain sense the flat tax game is over. As the old saying goes, from there on in we're just haggling over the price. Is there some natural law holding that having exactly two brackets is best? That strikes me as even more peculiar than insisting that there must only be one.

(3) Once Cain has agreed to put a zero rate in one of his three taxes, why not in the other two? Obviously, as an administrative matter one can't have a retail sales tax, or a quasi-VAT that has been mislabeled as a "business income tax," apply multiple brackets based on the income level of the individuals who purchase consumer goods. But doesn't the zero-rate feature that has now been added to Cain's personal tax imply that this is a defect one might want to address?

The so-called FAIR tax does so through what is effectively a demogrant, rather than a rate bracket. I've seen indications that Cain would like to have something of that nature in his 9-9-9 plan as well, but he hasn't made this entirely clear, and it would have significant budgetary / revenue implications unless its scope was trivial.

Cain also claims to add progressivity to his plan through an "opportunity zone" proposal. The idea, as described by CNN, is that "in cities facing high unemployment ... businesses could also deduct a certain amount of payroll expenses from their corporate taxes."

Enterprise zone features of income taxes generally have not received a hugely favorable write-up in the literature. In addition, if we can imagine Cain's proposals being adopted by Congress - and I certainly can't imagine this, even if he were to become president - it's hard to see why this special feature would be adopted and no others. Mightn't it open the floodgates? It's also fun to think about how the set of qualifying cities at any given time would be compiled, and whether businesses would be able to use this as a ground for deducting, say, high-end Wall Street salaries if New York qualified as an opportunity zone. Sure, one could start writing rules to address these problems, but by then (if not sooner) the 9-9-9 tax would be starting to look like a very different and more complicated animal.