How did you come up with 18%?
As a back of the envelope calculation if you spend 100% of income. Approximately right because the national savings rate is so low - but admittedly an approximation.
If Cain could pass his 999 I’d be happy, but I think we have reached the point politically that people will reject it because they don’t understand it or decide that it might adversely affect them (those calculations of embedded taxes are difficult for the average voter, who is intellectually quite lazy, to understand).