Why spread duration matters
It separates credit-spread sensitivity from government-rate duration and helps size credit risk, hedges, relative-value positions, and stress scenarios.
How it is applied
Analysts reprice the instrument after small spread shocks or derive sensitivity from cash flows, then aggregate market-value-weighted exposure across a portfolio. Estimate the percentage price change for a small parallel change in credit spread while holding the benchmark yield curve and modeled cash flows appropriately constant. Multiply spread duration by spread change for a first-order price approximation. Aggregate position contributions by market value for portfolio analysis.
Portfolio example
A bond with spread duration of four is expected to lose about 2% if its spread widens by 50 basis points, before convexity and other changes. A corporate bond has spread duration 5. If its credit spread widens 50 basis points, estimated price impact is minus 5 times 0.005, or minus 2.5%, before convexity, income, default, and any change in government yields.
How to interpret it
Higher spread duration means greater local price sensitivity to spread movement. It does not indicate whether spread is likely to widen or whether default will occur. Higher spread duration means greater sensitivity to changes in required credit compensation. Long maturities and low coupons often increase it. Interest-rate duration and spread duration can differ because government curves and credit spreads move separately.
Limitations and common misconceptions
The measure is linear and local. Options, distressed prices, curve shape, default, recovery, liquidity, and correlated rate moves require fuller revaluation and scenario analysis. The estimate is local and assumes a particular curve shift. Spreads can move nonparallel by maturity, sector, and rating. Callable, distressed, and structured securities require model-dependent cash flows. Spread widening may coincide with lower government yields, so total price movement need not equal the spread effect. Portfolio reporting can decompose spread-duration contribution by issuer, sector, rating, and maturity, revealing concentrations hidden by market value. Stress tests should combine wider spreads with default migration and reduced liquidity rather than moving spreads alone. For hedges, compare the spread duration and curve location of the hedge with the specific cash exposure.
Sources and further reading
- Fixed-Income Bond Valuation: Prices and YieldsCFA Institute