Just wondered if you have seen this article?
http://politicalticker.blogs.cnn.com/2011/10/09/cain-poor-wont-pay-more-under-9-9-9/
He assumes companies will give everyone a 15.3% pay increase, which I don’t believe would happen. Right now only 5.65% of your gross pay goes to Social Security and Medicare taxes. The other 7.65% is what the company pays, but there is no requirement that the company must give you that 7.65%.
That's wrong right off the bat. The overwhelming majority of people don't work for themselves. They pay a FICA that is currently 5.65%. That's less than 9% even before you factor in the 9% sales tax.
Cain explained that the proposed 9% national sales tax would only be applied to new goods that change hands and not to the sale of used goods
His own website makes no such claim. It speaks of a 9% sales tax, period. No exclusion for used goods or food or services or housing or anything. So virtually anything you buy goes up 9%.