Even if Warren become POTUS it will never happen. Congress will pass enough tax avoidances to get the bet effective tax rate down. A little history; during WWII The top tax rate was 90% but the net effective tax rate was about 19%. After WWII Truman cut the top tax rate to 70% but the net effective tax rate remained at 19%. JFK cut the top tax rate to 60% but the bet effective tax rate remained about 19%. Regean cut the top tax rate to 36% but the net effective tax rate remained about 19%. Currently top tax rate is about 36% but guess what, net effective tax rate is still about 19%. Bottom line, the sweet spot is about 19% and I’m guessing it will remain there.
He's not the originator of the concept but he popularized it beginning in the early 70s. I learned it at university working on my graduate degree in business.
Rates below 17% increase tax revenues but revenues start to come down if the tax rate is pegged at higher than 17%.
IOW, the actual maximum tax rates will still only produce revenues in the 17% tax rate range because of deductions, write-offs and loopholes.
But that 17% rate is pretty close to the 19% effective tax rate you state.
My memory of Laffer's curve and the specific rate he predicted would maximize government revenues may not be entirely accurate. It's been a few decades since graduate school.