Ignoring Duration Risk
Ignoring Duration Risk
A 30-year bond is not safe just because it is a bond. When rates rise, it falls faster and further than stocks.
Bonds are presented as the "safe" part of a portfolio. For income and principal stability, this is true relative to equities. But bonds carry a hidden risk that destroys this narrative: interest rate risk, measured by a metric called duration. Ignore duration, and you can lose 40% in a bond fund in a single year. That is not safer than stocks; it is just different damage.
Key takeaways
- Duration measures how much a bond's price falls when interest rates rise by 1 percentage point.
- A bond fund with 10-year average duration will lose 10% if rates rise from 4% to 5%.
- Long-duration bonds (20+ years) amplify losses in rising-rate environments; they fell 30–50% in 2022.
- Inverse relationship is permanent: higher rates = lower bond prices. No escape clause.
- Matching duration to your time horizon reduces the chance you must sell during an unfavorable rate environment.
What is duration?
Duration, measured in years, tells you approximately how much a bond's price will fall per 1 percentage point rise in interest rates. A bond with 5-year duration loses about 5% of price if rates rise by 1 point. A bond with 10-year duration loses about 10%. A bond with 20-year duration loses about 20%.
This math derives from the present-value calculation. A bond's value is the discounted sum of future coupons and principal. When the discount rate (interest rate) rises, future cash flows are worth less today. The longer you must wait for those coupons and principal repayment, the more the present value shrinks. A 30-year bond has cash flows extending far into the future, so its price is hyper-sensitive to discount-rate changes. A 2-year bond, with most coupons and principal arriving soon, barely budges when rates shift.
The 2022 catastrophe
In 2021, the 10-year Treasury yield sat at 1.5%. The Vanguard Total Bond Market Index (BND), tracking the entire U.S. bond market, had an average duration of about 6 years. An investor holding BND felt secure in "safe" bonds. But in 2022, the Federal Reserve raised rates from 0% to 4.33% in the fastest hiking cycle in decades. The 10-year yield shot from 1.5% to 4.2%. By simple duration math—a 2.7 percentage point rise on a 6-year-duration bond—BND fell roughly 16% that year. An investor who had $100,000 in BND on January 1, 2022, held only $84,000 by year-end, despite holding "safe" bonds.
Worse, many investors were in longer-duration funds. The iShares 20+ Year Treasury ETF (TLT), tracking U.S. government bonds with 20+ year maturities, has a duration around 17 years. When rates rose 2.7 points, TLT fell approximately 46%. An investor holding $100,000 in January fell to $54,000 by year-end. That is not portfolio "balance"; that is a catastrophic drawdown, and it happened in a fund marketed as "safe."
The inverse relationship is permanent
New investors often ask: "If bonds fall when rates rise, won't they recover when rates stabilize?" Yes, but with a caveat. Once rates stabilize at a higher level, bonds trade at their new, lower prices. If you hold to maturity, you receive your principal back, but you are locked into lower coupons than you would have earned had you bought after rates rose. If you must sell before maturity—to rebalance, pay a bill, or cover an emergency—you crystallize the loss.
The permanent part is this: the inverse relationship between interest rates and bond prices never changes. It is arithmetic, not opinion. A world of 6% Treasury yields is a world of lower bond prices than a world of 2% yields. There is no escape. The investor who chases high-yield bonds to avoid low coupons in a low-rate environment is still holding duration risk; they are just adding credit risk on top of it.
Duration and your time horizon
If your holding period exceeds the bond's duration, duration risk becomes irrelevant. A 10-year Treasury with 10-year duration falls if rates rise tomorrow, but if you hold for 10 years, you earn your promised 4% coupon regardless. Rates could spike to 6% the moment you buy, tanking the bond price, but you are not selling, so you do not crystallize the loss. Your yield-to-maturity is locked in.
This is why financial advisors pair bonds with their intended use. If you need money in 3 years, hold bonds with 3-year or shorter duration (Treasury bills, short-term bond funds, short-duration corporate bonds). Do not hold 10-year bonds and hope rates do not rise. If you need money in 10 years, hold 10-year bonds. If you will not need the money for 20+ years, long-duration bonds are acceptable—rates could rise, but you have the time to absorb them and still earn your coupons.
Duration varies across bond types
Not all bonds have the same duration. Here is how typical bond types line up:
- Treasury bills (3–12 months): 0.25–0.5 year duration. Essentially no interest-rate risk.
- Short-term bond funds (BIV, VBIRX): 2–3 year duration. Modest interest-rate risk.
- Intermediate bond funds (BND, VBTLX): 5–6 year duration. Moderate interest-rate risk.
- Long-duration Treasury funds (TLT, VGIT): 14–17 year duration. Severe interest-rate risk.
- Individual bonds held to maturity: Duration equals years to maturity (approximately).
- High-yield bonds: Lower duration (often 3–5 years) because the market values the sooner payoff, but credit risk offsetting.
An investor building a bond allocation must choose duration consciously, not by accident. "Bonds are safe" is true only if you have matched duration to time horizon and can avoid selling when rates are unfavorable.
Examples of duration in action
Suppose you hold three bonds, all yielding 4%:
- 2-year Treasury: 2-year duration. Rate rise to 5%: price falls ≈2%, to $98. Hold to maturity, earn 4% coupon.
- 10-year Treasury: 10-year duration. Rate rise to 5%: price falls ≈10%, to $90. Hold to maturity, earn 4% coupon.
- 30-year Treasury: 20-year duration. Rate rise to 5%: price falls ≈20%, to $80. Hold to maturity, earn 4% coupon.
If you are forced to sell one year after the rate rise, the 2-year bond is worth $98.50 (you are near maturity), the 10-year is worth around $91 (price has partially recovered as you approach coupon dates), and the 30-year is worth around $82. The longer-duration bond forces the largest loss. Conversely, if rates fall to 3%, the 30-year bond balloons to $120 in price, while the 2-year barely moves.
Building a ladder to manage duration
One technique to gain from bond income while managing rate risk is bond laddering: holding individual bonds with staggered maturities. An investor with $100,000 might buy $10,000 each of 1-year, 2-year, 3-year, ..., 10-year Treasuries. If rates rise and the 10-year falls sharply, the 1-year matures in a year and rolls into a higher-yield bond. If rates fall and the 1-year matures, you have just locked in low yields. On average, you earn a blended yield and are never fully exposed to the worst duration risk.
How it flows
The mistake: ignoring duration and assuming bonds are "safe"
Many investors hold long-duration bond funds while claiming safety. "Bonds are down 20% this year, but they are supposed to be safe." Correct. Bonds are safer than stocks over multi-decade horizons and during recessions. But in an isolated rising-rate environment, duration-heavy bonds are not safe in the short term. An investor with 30-year Treasury bonds as "ballast" in a portfolio that will be liquidated in 5 years has made a serious mistake. They are holding a 20-year-duration asset in a 5-year time horizon, guaranteeing pain if rates rise.
Related concepts
Next
The next article turns to credit risk: why high-yield and low-grade bonds behave differently than Treasuries, and how to distinguish between bonds where the yield premium compensates for danger versus bonds where you are overpaying for risk.