Interpreting Treasury Asset Swap Spreads as Relative Value
Summary
The document explains an asset swap spread as a measure of a Treasury bond’s relative performance against an interest rate swap of similar maturity. If the spread widens, the bond has underperformed the swap; if it narrows, the bond has outperformed. Comparing spreads across nearby Treasury maturities can also help identify relative value, although neighboring bonds generally differ only modestly and coupon-related measurement adjustments may matter.
The discussion links the spread to market structure: since Libor’s disappearance, swaps reference Sofr, an overnight repo rate, while Treasury yields also reflect supply and demand for government bonds. Issuance and other market forces can therefore move Treasury pricing relative to swaps. The author cautions that the interpretation is simplified and that numerous daily supply-demand influences remain. The piece does not provide a full asset-swap calculation or discuss all conventions and hedging mechanics, so it serves as an interpretation of the spread rather than a complete trading framework.
Key ideas
- An asset swap spread compares a Treasury bond’s yield with a similar-maturity swap rate.
- A widening spread indicates Treasury underperformance relative to swaps, while a narrowing spread indicates outperformance.
- Comparing spreads among nearby maturities can reveal relative value, though differences are often small.
- Treasury supply and demand can affect the bond’s value relative to swaps.
- Coupon differences and measurement conventions can complicate direct spread comparisons.
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Full text
# Asset swap on US treasury bond? # Asset swap on US treasury bond? I'm thinking through the asset swap spread between a US Treasury bond and a matched maturity swap rate (ATM) and had a question. I've heard that the asset swap spread is a measure of the bond's performance to "everything around it" on the yield curve, and to buy on asset swap is eliminating interest rate risk. Isn't it just relative to the fixed swap rate (e.g. bond outperforms swap, swap outperforms bond)? I think I'm missing the implication. ## Answer by dm63 (score 4) https://quant.stackexchange.com/a/82145 The asset swap spread is indeed a measure of the relative performance of a Treasury bond versus the matching maturity interest rate swap. For example the yield of a 10yr Treasury is currently around 4.30%, versus a 10yr swap at 3.88%. So the Treasury bond is equivalent to swaps + 42bp. If this spread increases to 50bp, then bonds have underperformed swaps , and if it decreases to 30bp, bonds have outperformed swaps. Some practitioners use this to discern relative value among different Treasuries. For example, if a 9.5 year bond were at swaps+ 48bp, it might look cheap versus the 10yr bond at 42bp. I believe that is what the 'all around it' statement you mention is probably talking about. Of course this is greatly exaggerated. Bonds close in maturity typically only vary by at most 1-2bp from their neighbors. There are some nuances in the measurement to adjust for high coupon bonds versus low coupons, but that would be a longer discussion. It is also important to consider the meaning of this spread. Why is the 10yr bond trading at a higher rate than the equivalent swap? Since the disappearance of Libor in 2023, interest rate swaps are based on Sofr, which is a default free overnight repo rate. The swap rate is essentially the market's projection for this overnight rate on average for the life of the swap. The yield on a Treasury, relative to the swap, represents supply and demand for Treasury bonds. In recent years, the US has been running a budget deficit and issuing a large amount of Treasuries, so their value has been declining versus swaps. This could reverse depending on government policy. There are many other supply and demand effects on a daily basis.
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