Subject: Re: In view of what's happening in Cali
A max tax rate of 20 % combined on LT capital gains would incentivize the superrich to realize significant unrealized capital gains and actually pay the tax.

Would it? Why? If you're Mark Zuckerberg or Jeff Bezos, there's no reason for you to ever realize your gains. You don't want the tax hit (whether 20% or not), and you don't want the loss of share ownership in your company that comes with selling.