Nominal Treasury Bonds vs. TIPS: What's the Difference?
Two government bonds can look nearly identical on paper — same issuer, same general safety profile — and still behave completely differently once inflation shows up. The difference comes down to whether the payment stream is fixed in dollar terms or adjusted as prices change.
The short answer
A standard treasury bond pays a fixed interest rate on a fixed principal amount, regardless of what happens to inflation afterward. TIPS, or Treasury Inflation-Protected Securities, instead adjust their principal value based on changes in a government price index, so both the principal and the resulting interest payments rise when inflation runs higher and fall when it runs lower. The two securities carry similar credit characteristics but very different exposure to how prices change over time.
How a nominal bond behaves
With a standard, or “nominal,” treasury bond, the coupon payment and the principal repaid at maturity are both set in dollar terms at issuance and don’t change afterward. If inflation runs higher than expected during the life of the bond, the purchasing power of those fixed payments erodes — the number of dollars stays the same, but what that money buys shrinks. If inflation runs lower than expected, or prices actually fall, the fixed payment holds its purchasing power better than anticipated, which works in the holder’s favor. This is the same basic mechanism described in how inflation affects money generally: fixed dollar amounts lose ground to rising prices.
How TIPS adjust differently
TIPS work by periodically adjusting the bond’s principal value in line with a government-published measure of price changes. The stated coupon rate is applied to this adjusted principal, so the actual dollar interest payment rises when the index rises and falls when the index falls. At maturity, the bond repays the greater of the inflation-adjusted principal or the original face value, which limits, though doesn’t eliminate, the downside if prices were to fall for an extended period. The tradeoff is that TIPS typically start with a lower stated coupon rate than a comparable nominal treasury bond, because part of the expected return is meant to come through the inflation adjustment rather than the coupon itself.
Why the “right” choice depends on what inflation does
- If inflation runs higher than the market expected, TIPS payments and principal adjust upward, generally outperforming a nominal bond of similar maturity over that stretch.
- If inflation runs lower than expected, or prices fall, the nominal bond’s fixed payments tend to look better in hindsight, since TIPS gave up some starting yield for protection that wasn’t needed.
- The market’s expectation of future inflation is already priced into both, through the gap between nominal and TIPS yields at issuance — so the comparison that matters isn’t whether there will be inflation, but whether it comes in above or below what was already expected.
Where duration and maturity still matter
Both types of treasuries are still bonds, and both are sensitive to interest rate changes through their duration. A TIPS holder isn’t protected from interest rate risk just because the security is inflation-adjusted — a rise in real interest rates can still push a TIPS bond’s market price down before maturity, separate from any inflation adjustment happening to its principal. The inflation protection addresses one specific risk, not every risk a bond carries.
What to weigh
Choosing between nominal treasuries and TIPS isn’t about picking the objectively better bond — it’s about which specific risk matters more for a given purpose. Someone weighing the two might consider what a future liability is denominated in, how long the money needs to stay invested, and how compensated they feel by the yield gap between the two types given their own risk tolerance. Because these are general mechanics rather than a recommendation for any specific portfolio, the right mix still depends on individual circumstances and current market pricing, which changes over time.