Pillar II • Fixed Income & Rates Microstructure
Interest Rate Swap Spreads: Why 30-Year Swap Spreads Turn Negative
Deconstructing the interest rate swap spread anomaly: why 30-year U.S. Treasury yields exceed SOFR swap rates, balance sheet capital costs, and pension ALM demand.
Author: CMD Wire Institutional Research
Updated: August 2026 • 7 min read
1. What Is an Interest Rate Swap Spread?
An Interest Rate Swap Spread is the difference between the fixed rate on an interest rate swap (where a market participant pays fixed and receives floating SOFR) and the yield of an on-the-run U.S. Treasury security of the same maturity:
$$\text{Swap Spread} = \text{Swap Fixed Rate} - \text{U.S. Treasury Yield}$$
Historically, swap spreads were always positive because interest rate swaps carry interbank counterparty risk, whereas U.S. Treasuries are backed by the full faith and credit of the sovereign. However, following the 2008 financial crisis, the 30-year U.S. swap spread collapsed into negative territory and has remained negative for over a decade.
2. The Institutional Drivers of Negative Long-End Swap Spreads
- Bank Regulatory Balance Sheet Constraints (SLR): Under Basel III Supplementary Leverage Ratio rules, primary dealers must hold 5%–6% equity capital against gross Treasury assets regardless of risk weighting. Owning a physical 30-year Treasury ties up precious balance sheet capacity, demanding a higher yield concession, whereas an interest rate swap is an unfunded derivative.
- Massive Treasury Coupon Supply: Trillion-dollar federal budget deficits have inundated primary dealers with long-dated 10Y and 30Y Treasury issuance, forcing Treasury yields higher relative to synthetic swap rates.
- Pension & Liability-Driven Investment (LDI) Demand: Defined-benefit pension funds and insurance companies receive fixed cash flows synthetically via long-dated swaps to match liabilities without having to fund cash purchases of Treasuries.