Uncertainty shocks steepen credit surfaces and raise leverage costs
Federal Reserve researchers John Geanakoplos and David Rappoport show that uncertainty shocks steepen corporate credit surfaces, raising borrowing costs for leveraged firms. Analyzing US bond data from 1998 to 2023, the study proves that credit spreads rise convexly with loan-to-value ratios.
Mapping spread curvature
The authors examine corporate bond market data from 1998 to 2023, covering 11,774 bonds issued by 3,100 domestic non-financial firms across five credit rating groups.
Using local linear kernel estimators, the empirical loan-to-value credit surface proves to be convex across rating categories.
During high volatility regimes, defined as months where the VIX index exceeds its 90th percentile of 29.4, credit surfaces shift upward and steepen sharply.
Average option-adjusted spreads for investment-grade bonds rated AAA to A- rise from 94 to 172 basis points, while spreads for high-yield bonds rated CCC+ to CCC- expand from 822 to 1,360 basis points, disproportionately impacting high-leverage borrowers.
The dual distribution language
To explain these empirical findings, the authors develop a mathematical framework for collateralized bond pricing.
They establish sufficient conditions for credit surface convexity across 12 standard distribution families, including log-normal, normal, gamma, and Weibull.
The study introduces the harmonic hazard rate order on dual loan insolvency distributions to formalize credit risk.
A central theoretical result proves that uncertainty shocks steepen loan-to-value surfaces across all leverage levels.
Beyond single-spread policy
Central bank models relying on a single credit spread overlook severe non-linear tightening during panics.
By showing how uncertainty penalizes high leverage, this framework delivers an essential tool for financial stability.
Policymakers must track the full credit surface rather than benchmark rates alone.