Scandinavian nations have the highest rates of high net worth individuals and billionaires per head. They also have high social mobility. Not bad for nations of high tax, unionised workforces and a strong welfare state.
It should be no surprise though should it? Nations that give everyone a chance to educate and show their brilliance, rather than nations that maintain an elite, have the highest rates of rich people. The cost of studying at degree level in the US keeps higher education relatively elite there.
(Unions also increase the need for automation and innovation in scandi countries as minimum wages are kept high, but the welfare state also ensures unions are not unreasonable, because workers always have a secure fallback with no job).