In general, greater income tax leads to greater wealth inequality.

The reason is, higher income tax means it is more difficult to become wealthy. So in countries with high income tax, the majority of wealthy people is those that inherited their wealth. Over time some wealthy people become poor, but with high income tax, even fewer become rich. This means that wealth becomes more and more concentrated among the few, which is somewhat counter-intuitive.

So in the US, wealth-mobility is greater than Denmark for example, resulting in the list on Wikipedia, where countries that are thought of as "unequal" actually are the most equal of all when it comes to wealth.

Article studying the effect: https://journals.plos.org/plosone/article?id=10.1371/journal...