Bond prices and interest rates move in opposite directions: when rates rise, existing bonds fall in value. Duration tells you exactly how much. A bond with a duration of 10 will lose roughly 10% for every 1% rate increase. Matching your bond duration to your time horizon is the decision that prevents painful losses.
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In October 2022, a retiree holding what her advisor had called a conservative bond portfolio checked her balance and found it down more than 25%. Her fund held long-term Treasury bonds: the safest securities on earth, backed by the full faith and credit of the United States government.1 She had not made a bad bet on a company. She had not bought junk. She had done everything right, according to the conventional wisdom that bonds are safe.
They are not safe. They carry a specific, often invisible risk that year made visible in the most painful way possible. Let's start with how that risk actually works.
The Machine: Why Bond Prices Move at All
When you buy a bond, you are making a loan. The borrower (a corporation, a city, the federal government) promises two things: regular coupon payments at a fixed interest rate, and the return of your full principal at maturity. If you hold the bond to maturity and the issuer doesn't default, you get exactly what was promised. The complication comes when you need to sell early, or when you own a bond fund that holds hundreds of bonds at varying stages of their lives.
Bond prices and interest rates move in opposite directions. This is not a preference or a prediction, it is arithmetic. Consider what happens when you buy a 10-year Treasury bond paying 3%, and six months later the Federal Reserve raises rates so that newly issued 10-year Treasuries pay 5%.2 Your bond still pays 3%. It has not changed. But any rational buyer comparing your 3% bond to a fresh 5% bond will only buy yours at a discount large enough that the total return (your lower coupon plus the gain from buying below face value) matches what the market is now offering. Your bond's price must fall until the math works out.
This is what finance calls the inverse relationship between bond prices and yields. The coupon rate printed on the bond stays fixed. The yield to maturity, which is what actually matters for comparison with everything else in the market, requires the price to move. Higher rates mean lower prices for all existing bonds, without exception.
Duration: The Number That Tells You Exactly How Much You Will Lose
Not all bonds suffer equally when rates rise. A 30-year Treasury and a 2-year Treasury are both backed by the U.S. government, but they behave very differently when rates move. Duration is the metric that captures this.3
Duration measures how much a bond's price will change for each 1% move in interest rates. The practical rule: multiply the duration by the rate change. A bond with a duration of 10 will fall roughly 10% in price if rates rise 1%. A bond with a duration of 5 will fall roughly 5%. A 30-year Treasury bond at today's rates carries a duration somewhere above 15. A 2-year Treasury's duration is barely above 1.
Two factors drive duration. The first is maturity: the further out you are waiting for your principal, the more sensitive the price is to rate changes. The second is coupon rate: a low-coupon bond returns less cash in the near term and more at maturity, which concentrates value in the distant future, so it swings harder on rate moves than a higher-coupon bond with the same maturity.
This matters most to people who own bond funds rather than individual bonds, which is most investors. When you buy an individual bond and hold it to maturity, the day-to-day price swings are irrelevant: you get back exactly what you were promised. But a bond fund never matures. It always holds bonds at market prices, which means it always carries duration risk. The average duration of the fund tells you almost exactly how hard it will swing when rates move.
A Real Scenario: The Math of 2022
Let's model what actually happened. Suppose you had $100,000 in a bond fund with an average duration of 12 years and a yield of 3% entering 2022. The Federal Reserve, facing inflation that peaked above 9%, raised the federal funds rate by 4.25 percentage points over that year.4 Long-term bond yields rose by roughly 2.3 percentage points as a result.
The price impact: 12 (duration) times 2.3% (rate increase) is a 27.6% price loss. Your fund collected roughly $3,000 in coupon income that year. Your net position at year end was somewhere around $75,000. A loss of $25,000 on a portfolio meant to be the safe part of your retirement savings.
This is not theoretical. The iShares Core U.S. Aggregate Bond exchange-traded fund (ETF), one of the most widely held bond funds in the country and a standard "safe" allocation for millions of retirement savers, fell roughly 13% in 2022. Funds holding only long-duration Treasuries did far worse. These were not exotic bets. They were the boring, responsible allocations.
The part most outlets skip is that the math cuts both ways. When the Federal Reserve began cutting rates in late 2024, long-duration bond prices recovered significantly. Duration is not a one-way trap. It amplifies moves in both directions. What you need to understand is that it does amplify them, and that holding 18-year duration when you need the money in five years is a mismatch that rate environments can expose brutally.
The Yield Curve and What It Signals
Bond investors watch something called the yield curve: a chart plotting the interest rates available on bonds of different maturities, from 1-month Treasury bills out to 30-year bonds.5 In normal times the curve slopes upward, because investors demand higher rates to lend for longer periods. A 10-year bond typically pays more than a 2-year bond, which pays more than a 3-month bill.
When short-term rates rise above long-term rates, the curve inverts. This has historically preceded every U.S. recession since the 1960s, though the timing has varied from months to nearly two years. The logic is straightforward: professional investors accept lower yields on long-term bonds when they expect rates to fall, and rates tend to fall when the economy weakens. An inverted curve reflects a collective bet that a slowdown is coming.
The Federal Reserve takes the yield curve seriously as a leading indicator. While it is not a guarantee, an inversion is one of the few signals in finance with a consistent historical track record. Watching the spread between the 2-year and 10-year Treasury yield gives you a read on what professional bond markets are pricing in about the economy's direction.
Credit Risk: The Other Danger
Interest rate risk affects all bonds, but credit risk is selective. Treasury bonds carry essentially no default risk: the U.S. government can tax and, ultimately, print dollars. Investment-grade corporate bonds carry more risk, priced into their higher yields relative to Treasuries. High-yield corporate bonds, often called junk bonds, offer still higher yields because the companies issuing them are more likely to struggle when the economy turns.6
Where this becomes a real problem is during recessions. High-yield bonds do not behave like Treasuries in a downturn. They fall alongside stocks as investors worry about companies defaulting on their debt. An investor who bought high-yield bonds for diversification discovers in the worst moment that the diversification was partial at best. The bonds that were supposed to hold steady while stocks fell are falling too.
This is not a reason to avoid high-yield bonds entirely. It is a reason to understand what you are actually buying. A fund labeled "bond fund" can hold anything from short-term Treasuries (minimal risk) to 20-year junk bonds (significant rate and credit risk combined). The label does not tell you which one you have.
Putting It Together: Matching Duration to Your Timeline
Here is what changes once you understand duration and credit risk: you can stop thinking about bonds as a safe/unsafe binary and start thinking about whether the specific bond risk you are taking matches your actual needs.
If you need the money in two years, short-duration bonds or Treasury bills are appropriate. You sacrifice yield, but the price sensitivity to rate changes is minimal: a 1% rate move on a bond with 1-year duration costs you about 1% in price, which the coupon income covers in a few months. If you are investing for 20 years, longer-duration bonds can make sense. You accept more short-term volatility for higher yields, and over a long horizon the income compounds while prices normalize.
The 2022 losses were not random bad luck. They were the consequence of investors holding durations of 12, 15, and 18 years in portfolios where the money was needed in 3 to 5 years. That mismatch was invisible during the 2010s, when rates were low and falling. It became devastating the moment rates rose sharply.
Bonds are a tool. They carry real, predictable mechanics. A bond with a duration of 10 years will lose roughly 10% for every 1% interest rate increase, and that is not a flaw in the bond; it is the price of holding a long-dated, fixed-rate instrument in a world where rates move. What you control is whether the duration of your bond allocation actually matches your time horizon. Get that right, and bonds do exactly what you need them to do.
