Earlier quoted context omitted.
Me in developing country sure see that billionaire's wealths already trickle down to developed country's citizens.
How can you be sure it’s not wealth trickling up instead?
So to me, it would be very hard to make an argument that it trickles up. It has to come from investment. And investment in the private sector is usually done by rich people, because you need money in the first place to invest and also because investing well makes you rich.