Goldman Sachs has pinpointed a single variable as the most important short-term risk across markets: long-end interest rates. When fiscal concerns are part of the instability, the safe-haven bid weakens, and long bonds lose their traditional insurance properties. A 100 basis point move in the 30-year yield translates to a price decline of roughly 15-20% on a zero-coupon bond of that maturity. If both sell off together because rising long-end yields hurt equities and fixed income simultaneously, the diversification benefit vanishes precisely when investors need it most. Goldman’s identification of long-end rates as the dominant risk factor is, in practical terms, a warning that this correlation breakdown could persist.