Inflation-Linked Bonds: Real Yields and Break-Even Inflation

What you will learn

• How inflation-linked bonds adjust principal and coupons with an index ratio.
• What a real yield is and how break-even inflation is calculated.
• When an inflation-linked bond does better or worse than a nominal bond.
• The main inflation-linked markets for euro investors and their specific risks.

Explanation

The macro course explained how inflation is measured and how to calculate a real return. This lesson shows a bond built around that idea.

An inflation-linked bond (a "linker") pays a fixed real coupon, but its principal is adjusted with a consumer price index. Because each coupon is paid on the adjusted principal, coupons grow with inflation too.

The index ratio

Index ratio = reference index on the payment date ÷ reference index at issue

Adjusted principal = face value × index ratio

Coupon = real coupon rate × adjusted principal

The reference index is usually taken with a lag of a few months, because price data are published later. Check the exact lag in each bond's terms.

Real yield and break-even inflation

The market yield of a linker is a real yield: the return above inflation if held to maturity. A normal (nominal) bond's yield includes expected inflation. The difference is the break-even inflation rate (BEI):

BEI ≈ nominal yield − real yield, or exactly (1 + nominal) ÷ (1 + real) − 1

If actual average inflation over the life of the bond is above the BEI, the linker does better than the nominal bond of the same maturity; if it is below, the nominal bond does better. BEI is not a pure inflation forecast: it also contains an inflation risk premium and a liquidity premium, because linker markets are smaller and harder to trade.

Main markets for euro investors

• Germany: inflation-linked federal securities are linked to the euro-area Harmonised Index of Consumer Prices (HICP) excluding tobacco. According to the German Finance Agency, they have not been issued or reopened since 2024; existing bonds remain tradable until maturity.
• France and Italy issue bonds linked to euro-area HICP excluding tobacco, and France also issues bonds linked to French inflation.
• United States: Treasury Inflation-Protected Securities (TIPS) are linked to the US consumer price index and pay coupons every six months; for a euro investor they add currency risk.

Deflation protection differs. TIPS repay at least the original face value at maturity, even if prices have fallen. Other linkers have their own rules, and coupons can fall when the index falls. Read the terms before you buy.

Risks

• Real-yield risk: if real yields rise, linker prices fall. Linkers have duration like any bond, and long linkers can lose a lot of market value even while inflation is high.
• Index mismatch: euro-area HICP may differ from your personal cost of living in Germany.
• Tax: the treatment of the inflation adjustment can differ from that of ordinary interest. For Germany, check with a Steuerberater.

Worked example

Hypothetical example: you buy €10,000 face value of a euro linker at issue (price 100). Real coupon 0.5%, paid annually. Reference index at issue: 100.0; one, two and three years later: 102.0, 105.5 and 109.0. The bond matures after year 3. Fees, spreads and taxes are excluded.

The principal kept its purchasing power: prices rose 9%, and so did the repayment.

Break-even comparison. A 10-year nominal government bond yields 2.6%, the 10-year linker of the same issuer yields 0.6% real.

• Approximate BEI = 2.6% − 0.6% = 2.0%.
• Exact BEI = 1.026 ÷ 1.006 − 1 = 1.99%.
• If inflation averages 3%: linker nominal return ≈ 1.006 × 1.03 − 1 = 3.62% a year, above the nominal bond's 2.6%.
• If inflation averages 1%: linker ≈ 1.006 × 1.01 − 1 = 1.61%, below 2.6%.

Common mistake

Practice activity

On paper, with hypothetical data: (a) A nominal bond yields 3.1% and a linker of the same maturity yields 1.0% real. Calculate the approximate and exact break-even inflation. (b) You hold €5,000 face value of a linker with a 0.75% real coupon. The reference index was 120 at issue and is 126 today. Calculate the adjusted principal and the coupon. (c) Expected inflation is 2.5%. Which bond would you expect to do better if your expectation is right?

Key takeaways

• Linkers pay a real coupon on a principal that is adjusted with an inflation index.
• Break-even inflation = the inflation rate at which nominal and linked bonds give the same return.
• A linker wins only if inflation turns out above the break-even rate.
• Rising real yields can cause price losses before maturity; deflation and tax rules differ by bond.

Next step

In the next lesson you will learn how to buy bonds in Germany in practice: exchanges, accrued interest and the real costs of a purchase.