|GDP data from the BEA; covering the span of 1930 - 2011|
One could argue that perhaps the above chart of GDP growth under the same year as the tax rate might not fully capture the impact because it may take time for changes in investment activity to filter into production of goods. So below let's look at a chart compiled by lining up the tax rates with the GDP growth for the year following the tax rate.
|GDP data from the BEA; covering the span of 1931 - 2011|
It's hard to get more clear than that. In both the same year and next year match-up scenarios, top marginal tax rates of 70% and above clearly correspond with higher GDP growth than top marginal tax rates below 70%. Indeed, during the Reagan years -- contrary to regressive notions -- lowered top marginal rates came with a corresponding drop in real GDP that manifested as a clear, year to year linear trending correlation. These correlations don't necessarily prove that the higher tax rates caused the higher GDP growth, but they certainly prove that lower tax rates have failed to fulfill the regressive claim. Judging from history, one can not reasonably expect that lowering upper bracket taxes will spur growth. And as Diamond and Saez have shown, there's no reason to expect lowering upper bracket taxes would increase our tax revenue either, since the optimal upper bracket rate for revenue collection sits far higher on the scale than where we are now, somewhere in the 70+% range.
If anything, the data suggests that raising upper bracket taxes may be more likely to spur growth. How could that be? The obvious answer is reinvestment. Lower upper bracket taxes encourage avoiding reinvestment to reap profit. Higher upper bracket taxes encourage reinvestment to avoid reaping taxable profit. That said, increasing upper bracket taxes alone will not fix everything. No matter how much tax policy encourages investment, there must be domestic market demand in order for domestic investment to make sense. Yet given enough demand to make domestic growth investments rational, higher upper bracket taxes can -- and logically will -- encourage that positive choice.