JAMES PETHOKOUKIS: The revenue and GDP impact of the Perry flat tax plan — now with actual numbers! “Under static scoring — assuming no growth impact from a more efficient, pro-investment tax code — the Perry Tax Plan (call it PTP-SS) would raise $4.7 trillion less than the Congressional Budget Office baseline forecast from 2014-2020. Of course, that forecast assumes all the Bush tax cuts expire, which is highly unlikely. Yet even under that scenario, revenue-to-GDP would be back to its historical average of around 18 percent of GDP by 2019.”