[AnthonyMouse]

> In that case, I suppose progressive income taxes are the only good way to have progressive taxation.

The key is to do progressive on the other side. Collect revenue with a flat consumption tax, then pay a uniform benefit, ideally a UBI.

If everybody pays a flat 30% tax rate and then everybody receives $10,000 in cash money, the effective tax rate for someone at $20,000/year is -20%. At $40,000 it's 5%. At $80,000 it's 17.5% and goes up from there.

So it's progressive but there is no arbitrage opportunity, no declaring profits in some other place, no weird cliffs or crazy high marginal rates on the poor due to benefits phase outs, the tax rate is uniform and applies the same to everyone without exception.