This is not a credible source for even the (vastly different from originally stated) claim that billionaires are more likely to hold title to inherited wealth “

This is not a credible source for even the (vastly different from originally stated) claim that billionaires are more likely to hold title to inherited wealth “now”: - it’s a survey. Rich people do not generally agree to do surveys. It’s a survey done by wealth management businesses looking for new clients - it’s a survey across an incredibly short time period, 9 years - it contains the quote “While more of new billionaires' overall wealth was generated by inheritance, the number of new self-made billionaires still surpassed the number of new billionaires who inherited the money.” Finally, most of the effect this link claims to measure is in mainland China. I do not think billionaires inheriting assets is the main policy failure of mainland China, and it doesn’t seem very relevant for a context where you said “As the majority of wealth in the US is now inherited”.