Where one asset class is mispricing macro risk against another. Each relationship regresses asset A on its structural driver B over ~2 years; the residual z-score measures how rich (z>0) or cheap (z<0) A trades versus what B implies. |z|≥2 is a dislocation — a mean-reversion edge and a tell that some market is out of line; |z|≥1.3 is stretched. This is where macro funds find asymmetric, low-beta money.