you've missed the point- the author doesn't independently confirm the existence the purported criminal- how do we even know the club to which he is a member even exists? how that institution requires every source in the world to divulge their wealth isn't examined by the author.
most non conspiratorial minded types would assume they use techniques similar to those that are used to estimate the extraction of iron, coal, etc.. While the numbers may not be spot on, it's hard to imagine they would be off to the point that a country like taiwan could amass twice the known reserves of the rest of the world.
then again, those masons are tricky fellows. /sarcasm
Nah, this is the work of the Build-a-burgers.
Indeed, and just to expand a bit, gold traders on the London markets have a vested interest in knowing as accurately as possible how much gold is out there floating around, since that directly affects the price of the gold they're trading. Do they know how much is produced, down to the last ounce? Of course not, but they spend a lot of time and a lot of money trying to get the best estimates they can - their livelihood depends on that kind of information. I also highly doubt that they somehow missed half of the world's gold supply before 1950.