I am probably not understanding something in the various wealth tax proposals: - How is wealth determined? The current billion numbers have a inverse relations

I am probably not understanding something in the various wealth tax proposals: - How is wealth determined? The current billion numbers have a inverse relationship with liquidation: The remaining stocks will lose value as more get sold. (Putting aside the capital gain aspect). - How is wealth loss captured? If my wealth was 1 Billion last year and it is 1 Million this year due to market crash, What happens? - How do we handle situation where the average through the period is lopsided? Say period is a year: What if my stocks were worth $1B in jan and $1MM in December?