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Real Interest Rates: Inflation, TIPS, and Valuation

For educational purposes only; not investment advice.

Direct answer

Section titled “Direct answer”

An ex ante real interest rate adjusts a nominal rate for expected inflation over the same horizon. The approximation is real rate ≈ nominal rate - expected inflation; the exact Fisher relation is real rate = (1 + nominal rate) / (1 + expected inflation) - 1. An ex post real rate substitutes realized inflation and is known only afterward. Maturity, currency, credit risk, compounding, and tax treatment must match before rates are compared.

How real rates are observed

Section titled “How real rates are observed”

Treasury Inflation-Protected Securities (TIPS) adjust principal using CPI-U, and their fixed coupon is applied to adjusted principal. A quoted TIPS yield is therefore a useful market real yield, but it is not a pure policy rate: liquidity, taxes, indexation lag, the deflation floor, and market positioning can affect it.

Same-maturity nominal Treasury yield minus TIPS real yield is the approximate breakeven inflation rate. It includes expected inflation plus inflation-risk and liquidity premiums, so it is not an exact inflation forecast.

Real rates influence saving, borrowing, investment, and the present value of inflation-adjusted cash flows. Nominal cash flows require nominal discount rates. Stock prices also reflect expected earnings and equity risk premiums, so a higher real yield does not mechanically imply a particular stock return.

Calculation example

Section titled “Calculation example”

With a 5% nominal rate and 3% expected inflation, the shortcut gives 2%; the exact result is (1.05 / 1.03) - 1 = 1.9417%. If realized inflation is 4.5%, the ex post real return is only (1.05 / 1.045) - 1 = 0.4785%.

If a 10-year nominal Treasury yields 4.2% and a comparable TIPS yields 1.7%, breakeven inflation is approximately 2.5%, not a guaranteed forecast. A real $100 cash flow due in 10 years is worth about $84.49 at a 1.7% real discount rate and $80.44 at 2.2%, before any cash-flow change.

Review checklist

Section titled “Review checklist”
  • Match observation date, maturity, compounding, currency, and credit quality.
  • Separate expected inflation from current or subsequently realized CPI.
  • Treat corporate yield minus inflation as credit-bearing, not a risk-free real rate.
  • Account for TIPS liquidity, taxes, indexation lag, accrued principal, and deflation floor.
  • Decompose breakevens conceptually into expectations, risk premium, and liquidity effects.
  • Discount real cash flows with real rates and nominal cash flows with nominal rates.
  • Ask why rates changed; growth, inflation, policy, and risk premiums may move together.

Common misconceptions

Section titled “Common misconceptions”
  • “Real rate always equals nominal rate minus current CPI.” Ex ante analysis uses expected inflation of matching horizon.
  • “TIPS yield is a pure Federal Reserve policy signal.” Market and security-specific effects remain.
  • “Breakeven inflation is the market’s exact forecast.” It contains premiums and technical distortions.
  • “A negative real rate guarantees asset gains.” Returns still depend on cash flows, valuation, and risk.
  • “Higher real rates always lower every stock.” Earnings expectations and risk premiums can offset discount-rate effects.
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Authoritative sources

Section titled “Authoritative sources”