It really doesn't matter. What matters is the result. The immediate result will be a windfall to the employee who now gets a bigger paycheck, but since the employer is still paying full wages and not saving a dime on employee cost, he can not lower the price of his goods very much. The price of goods may lower by 10% or so, but not nearly enough to make up for the 30% tax that will be charged. Unless all employees agree to take a pay cut, this plan is highly inflationary.The reason employees will want/need the employer's share of the payroll tax is that, if the FairTax is truely revenue neutral, the employee will be paying that tax someplace else. Either through higher tax inclusive prices, higher state and local taxes, or some other avenue. The tax has to be collected somewhere and the employee is going to need more nominal wages to pay it or his real wages (purchasing power) would be going down.
THe wage base is waaaaaaaaaaaaaaaaaaaay smaller than the consumption base.