A study by the Tax Policy Center
, a project of the center-left Brookings Institution and Urban Institute, claims that Mitt Romney's tax plan is mathematically impossible.
TPC claims that Romney cannot cut tax rates by 20 percent across the board and maintain revenue neutrality without raising the net tax burden on the middle class. According to TPC, in the year 2015 under Romney's tax plan, "maintaining revenue neutrality mathematically necessitates a shift in the tax burden of at least $86 billion away from high-income taxpayers onto lower- and middle-income taxpayers. This is true even under the assumption that the maximum amount of revenue possible is obtained from cutting tax expenditures for high-income households."
So, according to the Tax Policy Center, we start out with an $86 billion hole in Romney's tax plan. But the Tax Policy Center's own calculations show that that $86 billion hole can, in fact, be filled without raising middle class taxes.
TPC's study assumes that pro-growth tax reform cannot produce any economic growth. TPC acknowledges that, according to an economic model created by Harvard professors Greg Mankiw and Matthew Weinzerl that assumes tax reform will produce economic growth, "the tax cuts would result in revenue reductions of $307 billion (instead of $360 billion)." In other words, economic growth could fill $53 billion of that $86 billion hole.