> You made my point for me, thank you.

If your point is "we can't tax people because estimates aren't perfect", sure. But it's a silly point. We already tax people off estimates - if you own a house, your property taxes are assessed in exactly this fashion - an estimate of its value.

> It was "public knowledge" when his estimated net worth hit a trillion.

No. It was public knowledge when his known numbers of shares in his publicly traded companies reached a known price point.