If you want to know how little income tax billionaires are paying look at the disparity between the actual tax paid & the tax take from the posited 2% billionaires tax in the 2024 Global Tax Evasion Report.
Note: for billionaires, interestingly actually the USA is a relatively high tax country for the ultra rich (relative to others, not in absolute terms).
A globalised wealth tax however will be difficult to engineer (especially right now).
report:
https://www.taxobservatory.eu/www-site/uploads/2023/10/global_tax_evasion_report_24.pdf
