Banks Pledge Same Collateral Numerous Times
Big banks pledged the same mortgage to numerous people.
Similarly, big bullion banks borrow gold from central banks, and then rehypothecate it numerous times (see interview at link below)
(Options contracts on all commodities are similarly over-leveraged.)
A 1999 study by the International Monetary Fund found that 80 central banks lent out 15% of their official gold reserves.
Central banks now appear to have too little gold to meet their commitments.
And private banks are raiding allocated gold accounts