Real interest rates and inflation: what happens when rates trail CPI

The interest rate you see quoted — the Federal funds rate, the ECB deposit rate, the Bank Rate — is the nominal rate. What matters economically is the real rate: the nominal rate minus inflation. A 5% borrowing rate feels restrictive in a world of 2% inflation. The same rate feels stimulative when inflation is 8%.

This distinction is captured by the Fisher equation: real rate ≈ nominal rate − inflation. The more precise version is (1 + nominal) ÷ (1 + inflation) − 1. For policy analysis, the approximation is generally sufficient. The FRED 10-year real interest rate series, derived from TIPS yields, provides a continuous market-based real rate measure. The BIS publishes global real rate data across all major economies.

Why 2021–22 was so unusual

In mid-2022, US CPI hit 9.1% while the Federal funds rate was still at 2.5%. The real rate was approximately −6.6%. That meant: borrowing was effectively free (in real terms), saving was actively punished, and any investment earning a nominal return below 9% was losing real value.

Historically, the Fed tries to keep its real rate positive — above the neutral "r*" — when it wants to slow inflation. In 2021–22, with real rates deeply negative, monetary policy was accidentally super-stimulative even as nominal rates rose. That delayed the inflation-fighting effect of the initial rate hikes. The Brookings Institution has analysed this policy delay in detail.

The journey back to positive real rates

As central banks raised nominal rates aggressively from mid-2022 onwards — the Fed from 0.25% to 5.5%, the ECB from −0.5% to 4.0%, the Bank of England from 0.1% to 5.25% — and as inflation began to fall, real rates shifted from deeply negative to modestly positive. By October 2026, with inflation down and nominal rates high, real rates across the major economies are approximately:

United States: ~+1.35% (4.75% nominal − 3.4% CPI)
Euro area: ~+0.8% (4.0% nominal − 3.2% CPI)
United Kingdom: ~+0.9% (4.0% nominal − 3.1% CPI)

These are modestly restrictive. Whether they are sufficiently restrictive depends on where r* (the neutral real rate) lies — a concept we explain below. The ECB's projections and the Fed's FOMC projections both incorporate real rate assessments.

R-star: the neutral rate

R* (r-star) is the theoretical real rate at which monetary policy is neither stimulating nor restraining the economy. It cannot be directly observed — it must be estimated. The New York Fed's Holston-Laubach-Williams estimates put US r* at around 1–1.5%, meaning the current +1.35% US real rate is approximately at neutral — neither tight nor loose. The BIS has published extensive research on r-star's long decline from the 1980s and the debate about whether it has risen post-pandemic.

A central bank that keeps nominal rates stable while inflation falls is automatically tightening in real terms — even without a single rate hike.

Implications for savers and borrowers

For savers: a savings account paying 4.5% when inflation is 3.0% offers a real return of ~+1.5% — the first genuinely positive real savings return in many years. TIPS and UK index-linked gilts explicitly lock in real returns linked to CPI.

For borrowers: a mortgage at 5.5% with 3% inflation has a real rate of +2.5% — significantly more expensive in real terms than a 3% mortgage during 6% inflation (real rate: −3%). The UK's housing market has felt this sharply, with mortgage affordability worsening even as nominal rates remain below their 2023 peak.

See also our glossary entries on real interest rate, purchasing power, and PCE price index.

Frequently asked questions

What is the real interest rate?

The real interest rate is the nominal rate minus the inflation rate — what a saver or borrower actually gains or loses in purchasing power. With the Fed funds rate at 4.75% and CPI at 3.4%, the US real rate is approximately +1.35%. The FRED 10-year real rate series gives a market-based view derived from TIPS yields. Our glossary entry on real interest rates covers the theory in full.

Why were real interest rates so negative in 2021–22?

Central banks kept nominal rates near zero through 2021, having slashed them in response to the COVID-19 pandemic. When inflation surged — first due to supply chain disruptions, then the energy shock — the gap between nominal rates and inflation widened dramatically. The Fed's real rate hit approximately −6.6% in mid-2022. The Brookings Institution and the IMF have published detailed analyses of this episode.

What is r-star (the neutral real rate)?

R-star (r*) is the theoretical real interest rate consistent with an economy running at full employment with stable inflation — neither expanding too fast nor contracting. It is the benchmark for whether monetary policy is "tight" or "loose". The New York Fed publishes quarterly Holston-Laubach-Williams r-star estimates. Current US r* is estimated at around 1–1.5%, suggesting the current real rate of ~+1.35% is approximately neutral. The BIS and OECD also publish r-star research.

How do real interest rates affect inflation?

Positive real rates increase the cost of borrowing in real terms — reducing incentives to take out loans, buy on credit, or invest in new capacity. This reduces aggregate demand, which over time brings inflation lower. Negative real rates do the opposite: they subsidise borrowing, encourage spending, and can amplify inflation. The ECB, Fed, and Bank of England all publish their frameworks for how rate decisions transmit to inflation.

What is a TIPS and how does it show real interest rates?

Treasury Inflation-Protected Securities (TIPS) are US government bonds with principal adjusted by CPI. Their yield is a direct measure of the real interest rate: investors accept a lower nominal yield because their principal preserves real purchasing power. The spread between a regular Treasury and a TIPS of the same maturity is the "breakeven" inflation rate — the market's implied inflation expectation. The UK equivalent is index-linked gilts. FRED publishes the 10-year breakeven series in real time.