“What’s to keep them from just upping the rate like the states do?”
The founders got it right!
“It is a signal advantage of taxes on articles of consumption, that they contain in their own nature a security against excess. They prescribe their own limit; which cannot be exceeded without defeating the end proposed, that is, an extension of the revenue. When applied to this object, the saying is as just as it is witty, that, ‘in political arithmetic, two and two do not always make four.’ If duties are too high, they lessen the consumption; the collection is eluded; and the product to the treasury is not so great as when they are confined within proper and moderate bounds. This forms a complete barrier against any material oppression of the citizens by taxes of this class, and is itself a natural limitation of the power of imposing them.”
Alexander Hamilton in Federalist #21
It is very likely that every man, woman and child would know what the tax rate was before the FairTax was ever implemented. After all, there would be at least a 6 month delay between its enactment in congress and its implementation date. Can you imagine the pressure on congress to reduce the rate if everyone were paying the same rate on everything?
There’s that GMTA thing again. :)