Data AnalysisUpdated 875 words, 4 minutes
Mortgage rates and the 10-year Treasury: the spread since 1971
The 30-year fixed mortgage rate minus the 10-year Treasury yield, every survey week since 1971, by decade and year, with the widest and narrowest weeks.
The 30-year mortgage rate is often described as "the 10-year Treasury plus a spread". This article measures that spread every survey week from April 1971 to September 2026, so that "the spread is wide" or "the spread has normalised" can be checked against 2,893 numbers instead of a feeling. The dataset and the script are attached, and every figure below is printed by the script.
The data
MORTGAGE30US: Freddie Mac's Primary Mortgage Market Survey average 30-year fixed rate, weekly, dated on the Thursday of the survey week, in percent. The FRED series page notes that on 2022-11-17 Freddie Mac changed the survey method to be based on applications submitted to Freddie Mac by lenders, rather than the earlier lender survey.DGS10: the 10-year constant-maturity Treasury yield from the Federal Reserve's H.15 release, daily, in percent.
Both retrieved from FRED on 2026-09-05. The mortgage series begins on 1971-04-02; the last survey week in the file is 2026-09-03.
The method
For each survey Thursday, the script takes the 10-year yield on that date. If the Treasury market was closed that day (Thanksgiving is the usual case), it uses the most recent earlier close. The spread is the mortgage rate minus that yield, in percentage points.
dgs = df["DGS10"].ffill() # carry the last close over holidays
w = df["MORTGAGE30US"].dropna().to_frame("mort")
w["dgs10"] = dgs.reindex(w.index) # the 10-year on each survey Thursday
w["spread"] = w["mort"] - w["dgs10"]
Forward-filling the Treasury series before reindexing is the whole trick. Reindexing without it drops any week where the Thursday was a holiday and quietly shrinks the sample.
The tables
Output of python code/mortgage-rate-10-year-spread.py on 2026-09-05.
| decade | weeks | mean spread (pp) | median | narrowest (week) | widest (week) |
|---|---|---|---|---|---|
| 1970s | 457 | 1.34 | 1.28 | 0.45 (1975-08-15) | 2.60 (1979-12-07) |
| 1980s | 522 | 2.12 | 1.96 | -0.03 (1980-02-22) | 5.66 (1980-05-02) |
| 1990s | 522 | 1.45 | 1.42 | 0.97 (1996-03-08) | 2.46 (1998-10-16) |
| 2000s | 522 | 1.83 | 1.78 | 1.23 (2009-12-24) | 3.11 (2008-12-18) |
| 2010s | 521 | 1.69 | 1.68 | 1.08 (2010-03-25) | 2.37 (2011-09-22) |
| 2020s | 349 | 2.26 | 2.34 | 1.28 (2021-05-13) | 3.26 (2022-11-10) |
By year, for the recent period:
| year | mean mortgage rate | mean 10-year yield | mean spread (pp) |
|---|---|---|---|
| 2018 | 4.54 | 2.91 | 1.64 |
| 2019 | 3.94 | 2.14 | 1.80 |
| 2020 | 3.11 | 0.90 | 2.21 |
| 2021 | 2.96 | 1.45 | 1.51 |
| 2022 | 5.34 | 2.95 | 2.39 |
| 2023 | 6.81 | 3.96 | 2.85 |
| 2024 | 6.72 | 4.21 | 2.51 |
| 2025 | 6.60 | 4.29 | 2.30 |
| 2026 | 6.37 | 4.40 | 1.96 |
Whole sample: mean 1.76 points, median 1.67. The widest week was 5.66 points on 1980-05-02 and the narrowest was -0.03 on 1980-02-22, ten weeks apart. The latest week, 2026-09-03, has a mortgage rate of 6.71, a 10-year yield of 4.77, and a spread of 1.94. The 2026 row covers January through the first week of September.
What it shows
The long-run centre of the spread is about 1.7 points, and most decades sit within a few tenths of it. Two periods stand out above that centre. The first is 1980 to 1982, which contributes both extremes of the whole record: the spread went from slightly negative in February 1980 to 5.66 points in May 1980 as Treasury yields fell far faster than mortgage rates. The second is 2022 to 2024, when the yearly mean reached 2.85 points in 2023, the highest calendar-year mean in the file, and 45 percent of survey weeks since the methodology change of November 2022 have printed above 2.50 points.
The 2020s row is the only decade with a mean above 2.2, and 2023 was the peak: 84 weeks in the whole record have a spread above 3.00 points, and the widest of the recent era, 3.26 on 2022-11-10, is the third-highest week since 1982 after the 2008 crisis weeks. Since then the yearly mean has fallen each year, from 2.85 to 2.51 to 2.30 to 1.96 in 2026 to date, which puts 2026 back inside the range of the 2010s (mean 1.69) rather than above it. The mean from 2010 to 2019 is 1.69 and from 2023 to date it is 2.45.
The year rows also show that the level of the mortgage rate is mostly the level of the 10-year. In 2021 the mean mortgage rate was 2.96 with a spread of 1.51; in 2025 it was 6.60 with a spread of 2.30. Of the 3.64-point rise, 2.84 points came from the Treasury yield and 0.79 from the spread.
What it does not show
The spread is not a single thing. It bundles the option-adjusted spread on mortgage-backed securities, servicing and guarantee fees, lender margins, and the difference between a 30-year amortising loan's expected life and a 10-year bullet bond. This table does not decompose it; when the spread widened in 2022 and 2023 the table cannot say how much was prepayment-risk pricing and how much was lender pricing.
The Thursday match is an approximation. The survey collects rates across the week, and the Treasury yield can move a lot between Monday and Thursday in a volatile week. The 1980 extremes are partly an artefact of that timing at a moment when yields were moving by tens of basis points a day.
The 2022-11-17 methodology change means the series before and after are not measuring exactly the same rate. The FRED notes state the change; they do not quantify its effect, and neither can this article.
None of this predicts where the spread goes. A reversion toward 1.7 is what the history looks like on average, and 2026 to date is close to it, but the 1980s and the 2020s are reminders that the average is not a bound.