These "top rich lists" are generally calculated on public net worth... that is, if they were able to sell all of their current possessions (including companies, land, etc) for what their appraised value currently is, X is the amount of money they'd have... and how much they're 'worth'.

Note, again, that that's PUBLIC net worth... many sultans and political figures in the middle east prefer not to be particularly public about their wealth, other than utilizing some very expensive assets (cars, palaces, etc).


Someone once illustrated (and it might have been Gates himself) that if he dropped $1000 on the ground while on the way to work, it would not be worth his time to pick it up.