I think some people have amnesia. I’ve heard several times over the last few months that several politicians (namely Ryan & crew) are espousing a return – or more accurately an acceleration – of supply-side policies while claiming it will increase economic growth. This is the equivalent of arguing who will win the 1991 World Series title, we have plenty of data to show the outcome. I think the nonpartisan Congressional Research Service (CRS) report did a great job showing the numbers and findings when a reasoned eye looks at all the data:
The results of the analysis suggest that changes over the past 65 years in the top marginal tax rate
and the top capital gains tax rate do not appear correlated with economic growth. The reduction in
the top tax rates appears to be uncorrelated with saving, investment, and productivity growth. The
top tax rates appear to have little or no relation to the size of the economic pie.However, the top tax rate reductions appear to be associated with the increasing concentration of
income at the top of the income distribution. As measured by IRS data, the share of income
accruing to the top 0.1% of U.S. families increased from 4.2% in 1945 to 12.3% by 2007 before
falling to 9.2% due to the 2007-2009 recession. At the same time, the average tax rate paid by the
top 0.1% fell from over 50% in 1945 to about 25% in 2009. Tax policy could have a relation to
how the economic pie is sliced—lower top tax rates may be associated with greater income
disparities.
TL;DR – Decreasing tax rates on the wealthy will not spur economic growth, it will simply increase income disparity.