What is Duration? (Plain English Definition)
Definition: Duration measures a bond or bond fund's sensitivity to interest rate changes, expressed in years -- the higher the duration, the more the price moves when rates change.
Duration Explained Simply
Duration is a measure of how sensitive a bond or bond ETF is to changes in interest rates. It is expressed in years, but think of it as a risk indicator rather than a time period. A bond ETF with a duration of 6 years will lose approximately 6% of its value if interest rates rise by 1 percentage point, and gain approximately 6% if rates fall by 1 percentage point.
There are several types of duration, but the most commonly used for ETF investors is effective duration. Short-duration bond ETFs (duration under 3 years) are relatively stable and less affected by rate changes. Intermediate-duration funds (3-7 years) offer a balance of yield and stability. Long-duration funds (10+ years) offer higher yields but can experience dramatic price swings when interest rates move.
Duration is the single most important risk metric for bond ETF investors. Even high-quality Treasury bond ETFs can lose significant value if interest rates rise sharply. In 2022, when the Federal Reserve raised rates aggressively, long-term Treasury ETFs lost over 30% of their value despite holding the safest bonds in the world.
Duration Example
You hold two bond ETFs: one with a duration of 2 years and another with a duration of 15 years. If interest rates rise by 1%, the short-duration fund loses about 2% while the long-duration fund loses about 15%. On a $50,000 investment in each, that is a $1,000 loss versus a $7,500 loss. The long-duration fund offers higher yield to compensate for this risk, but the potential for larger losses is significant.
Why Duration Matters for ETF Investors
Duration is arguably the most critical number to check before buying any bond ETF. It tells you exactly how much interest rate risk you are taking on. Many investors learned this lesson painfully in 2022 when rising rates caused even "safe" bond funds to suffer substantial losses. For ETF investors, matching duration to your time horizon is a sound approach. If you need the money in 2-3 years, short-duration bond ETFs minimize the risk of losses from rate increases. If you are investing for 10+ years, you can tolerate longer-duration funds that offer higher yields, knowing that any interim losses will likely be recovered over time.
Duration vs Bond
| Duration | Bond |
|---|---|
| Duration measures a bond or bond fund's sensitivity to interest rate changes, expressed in years -- the higher the duration, the more the price moves when rates change. | See full definition of Bond |
While duration and bond are related concepts, they serve different purposes in the world of ETF investing. Understanding both terms helps you make more informed decisions about which funds to include in your portfolio and how to evaluate their performance.
Related Terms
Deepen your understanding of ETF investing by exploring these related concepts:
Bond
A bond is a fixed-income investment where you lend money to a government or corporation in exchange for regular interest payments and the return of principal at maturity.
Interest Rate
An interest rate is the cost of borrowing money or the return earned on lending money, expressed as a percentage of the principal amount.
Fixed Income
Fixed income refers to investments that provide regular, predictable interest payments, primarily bonds and bond-like securities.
Yield to Maturity (YTM)
Yield to maturity is the total return anticipated on a bond if held until it matures, accounting for coupon payments, current price, and the face value received at maturity.
Maturity
Maturity is the date on which a bond's principal is repaid to the investor and interest payments cease.
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