Why Spread Duration Is Scaled by Spread but Yield Duration Is Not

Summary

The note asks why fixed-income practitioners use duration times credit spread, often called spread duration times spread, while an equivalent duration-times-yield measure is uncommon. It compares the rationale given for spread duration times spread with the behavior of yield volatility.

The answer argues that the scaling assumption behind the spread measure does not transfer to yields. Relative spread volatility is presented as more stable than absolute spread volatility, whereas yield volatility has not reliably moved in proportion to yield. The possibility of negative yields is offered as an illustration of why proportional scaling is unsuitable. The note gives no empirical dataset, derivation, or detailed supporting analysis, so it serves as a concise conceptual explanation rather than a full validation of the claim.

Key ideas

• Spread volatility may be more stable when expressed relative to the spread level.
• Yield volatility has not consistently scaled with the yield level.
• The occurrence of negative yields illustrates the limitations of proportional yield scaling.
• The explanation is brief and does not provide supporting data or a formal derivation.

Tags

# Why do people use (spread) Duration times spread (DTS) but no one uses (yield) duration times yield?


# Why do people use (spread) Duration times spread (DTS) but no one uses (yield) duration times yield?












According to the DTS paper, the argument for using DTS instead of spread duration itself is that relative spread volatility is more stable than absolute spread volatility. Then surely the same argument applies on yield as well. So why do people not use duration times yield?

## Answer by Mats Lind (score 1)

https://quant.stackexchange.com/a/29527

Yield volatilities have not turned out to scale with yield. Otherwise yields would not have managed to become negative. The paper claims though that spread vol scales well with spread. Hence there are no similar arguments to apply .

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