1. I think AOC is proposing a 70% rate for personal income taxes.
Whether corporate or personal, if USA rates are dramatically raised loopholes will be inserted into the tax code to allow rich to avoid paying the higher rates.
2. Here is the data on effective tax rates paid by the top 1% of income earners.
3. The claim of the Laffer Curve is theoretical. The claim is that there is an “optimal” income tax rate, one which maximizes government tax revenue. It doesn’t make an empirical prediction about what the “optimum” tax rate is and so, it can’t be tested by the empirical results of tax rate changes. It’s true that Laffer himself thought the 1980s income tax rates were above the “optimal” rate, but that was just his guess.