I would be very cautious drawing any firm conclusion from this kind of simplistic analysis.
First, as always with economic analysis, many other things are changing at the same time (inflation, trade, technology, etc.). Any one or some combination of other factors could actually be driving this and you would not know it. Additional event studies and evidence from other countries would be a start.
Second, you are effectively cherry picking your sample periods. 1936 was the very bottom of the Great Depression. Why don't we also look at the period before the US had income taxes, other countries, etc.
Third, tax rates are only one part of tax policy. Effective tax rates would be a start but then how to measure income when there is a big incentive to hide it.
Lastly and probably most importantly, what is the logic here. How exactly do high tax rates increase growth. It makes sense that they would reduce incentives. How much money would it raise? And if there is some great spending projects that increase growth why aren't we already doing them?
First, as always with economic analysis, many other things are changing at the same time (inflation, trade, technology, etc.). Any one or some combination of other factors could actually be driving this and you would not know it. Additional event studies and evidence from other countries would be a start.
Second, you are effectively cherry picking your sample periods. 1936 was the very bottom of the Great Depression. Why don't we also look at the period before the US had income taxes, other countries, etc.
Third, tax rates are only one part of tax policy. Effective tax rates would be a start but then how to measure income when there is a big incentive to hide it.
Lastly and probably most importantly, what is the logic here. How exactly do high tax rates increase growth. It makes sense that they would reduce incentives. How much money would it raise? And if there is some great spending projects that increase growth why aren't we already doing them?