That's the conclusion of this new Congressional Research Service study:
not conclusive evidence … to substantiate a clear relationship
between the 65-year steady reduction in the top tax rates and economic
growth. Analysis of such data suggests the reduction in the top tax
rates have had little association with saving, investment, or
productivity growth. However, the top tax rate reductions appear to be
associated with the increasing concentration of income at the top of the
income distribution. 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. The evidence does not
suggest necessarily a relationship between tax policy with
regard to the top tax rates and the size of the economic pie, but there may be a relationship to how the economic pie is sliced.
Talking Points Memo has this story on the report.