Short answer. The 30-year fixed mortgage rate is primarily determined by the yield on 10-year U.S. Treasury bonds plus a spread for mortgage-backed security (MBS) credit risk and lender margin. The Federal Reserve does not set mortgage rates directly, though its actions strongly influence the Treasury market.
| Factor | Direction | Typical Impact |
|---|---|---|
| 10-year Treasury yield rises | ↑ rates | Primary driver |
| Fed raises funds rate | ↑ rates | Indirect via bond market |
| MBS demand increases | ↓ rates | Spreads compress |
| Inflation expectations rise | ↑ rates | Via Treasury yields |
| Credit risk increases | ↑ rates | Spreads widen |
There is widespread confusion about the relationship between the Federal Reserve and mortgage rates. The Fed sets the overnight federal funds rate — the rate banks charge each other for overnight lending. Mortgage rates are longer-term instruments that track a different part of the yield curve.
The 10-year Treasury connection
The 30-year fixed mortgage rate moves most closely with the 10-year U.S. Treasury yield because mortgages are prepaid on average in 7–10 years (even though the amortization period is 30 years). Lenders and MBS investors price mortgages relative to the 10-year Treasury as the risk-free benchmark. Historically, the 30-year mortgage rate has averaged roughly 150–200 basis points (1.5–2.0 percentage points) above the 10-year Treasury yield.
The MBS spread
Most U.S. mortgages are securitized into mortgage-backed securities (MBS) issued by Fannie Mae, Freddie Mac, or Ginnie Mae. MBS investors require a spread above Treasuries to compensate for prepayment risk (borrowers refinancing early when rates fall) and convexity risk. When this spread widens — as it did in 2022–2023 — mortgage rates rise faster than Treasury yields alone would suggest. The MBS spread was unusually wide in 2023, adding ~60 basis points above historical norms.
The Fed's indirect influence
The Federal Reserve influences mortgage rates through two channels: (1) setting short-term rates, which ripple through to longer-term rates via expectations; and (2) buying or selling MBS directly (quantitative easing/tightening). Between 2020 and 2022, the Fed bought $1.4 trillion in MBS, compressing spreads and keeping mortgage rates at historic lows. When it stopped buying and began reducing its MBS holdings in 2022, spreads widened and rates jumped even faster than the federal funds rate hikes alone would have caused.
Data context
In 2021, the 30-year fixed rate averaged 2.96% against a 10-year Treasury averaging ~1.45% — a spread of roughly 151 basis points. In 2023, the rate averaged 6.81% against a 10-year Treasury averaging ~4.0% — a spread of roughly 281 basis points, reflecting both elevated MBS spreads and Fed QT.
Sources
Freddie Mac Primary Mortgage Market Survey; Federal Reserve Bank of St. Louis FRED 10-year Treasury Constant Maturity Rate; Federal Reserve Board monetary policy communications; Urban Institute Housing Finance Policy Center.
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