By 1971, the Eurodollar market — US dollar deposits held outside the United States, mostly in London — had grown to an estimated $50–70 billion, dwarfing official gold reserves of ~$10 billion. These offshore dollars were unregulated by the Fed, paid no reserve requirements, and could be created by foreign banks simply by booking deposits. This parallel money supply made Bretton Woods structurally unenforceable.

The mechanics worked like this:

Foreign central banks accumulated dollars from trade surpluses and parked them in London
London banks re-lent those dollars globally, multiplying claims on US gold
When France or Germany demanded conversion, the US faced a run it could not service
Nixon's closing of the gold window on August 15, 1971 was a recognition that the offshore dollar pool exceeded any feasible gold backing

Year	US Gold Stock ($B)	Foreign Dollar Claims ($B)	Coverage Ratio
1950	22.8	8.0	2.85
1960	17.8	18.7	0.95
1968	10.9	33.0	0.33
1971	10.2	60.0	0.17

The coverage ratio collapse from 2.85 to 0.17 in two decades shows the Triffin Dilemma in hard numbers: supplying global liquidity required running deficits that destroyed confidence in convertibility.