The European Central Bank published Economic Bulletin research examining why US non-financial corporate bond spreads stayed unusually compressed through 2024 despite elevated interest rates, and what the subsequent abrupt widening could imply. The analysis notes that spreads have recently repriced sharply, alongside a deterioration in market risk sentiment following the US administration’s announcement of new tariffs, with investment-grade spreads rising to 120 basis points and high-yield spreads to 461 basis points. Through 2024, investment-grade spreads ranged between 83 and 112 basis points and high-yield spreads between 264 and 393 basis points, placing both near the lowest levels in almost two decades. The box attributes much of the earlier compression to strong risk-on sentiment and robust earnings expectations, with excess bond premium estimates pointing to persistently high investor risk appetite since late 2022 and nearly 90% of bonds trading below levels implied by firm-specific fundamentals through end-February 2025. Composition effects also mattered in high yield, where issuance has shifted towards higher-quality BB-rated bonds, while riskier B-rated issuance has declined and CCC or below has remained low. Looking ahead, the ECB highlights rollover and repricing risks given USD 642 billion of corporate debt maturing in the rest of 2025, USD 930 billion in 2026, and USD 860 billion in 2027, with simulations suggesting 85% of maturing debt would be refinanced at higher rates and more than half facing increases above 1 percentage point at current rates. It also finds that in risk-off episodes spreads become more sensitive to shocks and widening is disproportionately concentrated among firms with weaker financing conditions relative to fundamentals, while expected default frequencies signal emerging tail vulnerabilities, with the 75th percentile reaching around 18% at end-March 2025.