The chart displayed above shows top tax rates on long-term capital gains and economic growth (measured as the percentage change in real GDP) from 1950 to 2011. If low capital gains tax rates catalyzed economic growth, you’d expect to see a negative relationship–high gains rates, low growth, and vice versa–but there is no apparent relationship between the two time series. The correlation is 0.12, the wrong sign and not statistically different from zero. I’ve tried lags up to five years and also looking at moving averages of the tax rates and growth. There is never a statistically significant relationship.