What is the spread duration for non-callable fixed rate corporate bonds?

Spread duration for non-callable fixed rate corporate bonds is generally considered to be approximately equal to the modified duration. Modified duration measures the sensitivity of a bond's price to changes in interest rates, specifically reflecting the percentage change in the price for a 1% change in yield. Since non-callable bonds have fixed cash flows and are less complex in their structure, the modified duration serves as a suitable measure for understanding how changes in credit spreads will affect their prices.

By using modified duration as a point of reference for spread duration, investors can assess the risk associated with changes in credit spreads in relation to their total return expectations. The approximation is particularly valid because non-callable bonds are exposed primarily to interest rate risk rather than embedded options that could complicate their duration measures.

In contrast, other options such as duration equal to the yield, duration adjusted for credit risk, or average time to maturity do not accurately capture the essential characteristics of spread duration for these types of bonds. Each of those has a different set of implications regarding bond valuation and risk assessment that does not align with the straightforward nature of non-callable fixed-rate bonds.