People buy government bonds for safety. Then a period arrives when rates rise sharply and those bonds — issued by a government that will unquestionably repay them — fall by double digits. Investors who understood they were taking no credit risk discover they were taking a different risk nobody named for them.
That risk has a measurement, and it is printed on every bond fund's fact sheet. Duration tells you roughly how much value moves when rates move, and it is arguably the most useful number in fixed income.
What changed in 2026
- The lesson stayed fresh. A sharp rate-rise cycle within recent memory left duration far better understood among ordinary investors than it was a decade ago.
- Short-duration products got popular. Money market funds and short-term bond funds absorbed large flows from investors who had learned the difference the hard way.
- Defined-maturity bond ETFs grew. Funds holding bonds maturing in a specific year gave fund investors something closer to an individual bond's maturity date.
- The mechanics did not change. Duration works the way it always has. What changed is how many people have experienced it.
What duration measures
A bond pays fixed amounts on a fixed schedule. If prevailing rates rise, newly issued bonds pay more — so an existing bond paying less must fall in price until its return is competitive. If rates fall, the reverse.
Duration estimates the size of that move. As a rule of thumb, price change ≈ −duration × change in rates.
A fund with a duration of 7 loses roughly 7% if rates rise one percentage point, and gains roughly 7% if they fall one. A duration of 2 moves about 2%. This is an approximation that degrades for large moves, and it is close enough to be genuinely useful.
| Duration |
1% rate rise |
Typical holding |
| ~0.5 |
~0.5% loss |
Money market, ultra-short |
| ~2 |
~2% loss |
Short-term bond fund |
| ~6 |
~6% loss |
Intermediate / total bond market |
| ~17 |
~17% loss |
Long-term government bonds |
That last row explains how "safe" holdings produced losses people associate with equities. Long-dated government bonds have enormous duration, and a few percentage points of rate rise is a very large move against them.
Duration rises with time to maturity and falls with the size of the coupon — a bond returning more of its value sooner is less sensitive. Zero-coupon bonds, returning everything at the end, have the highest duration for their maturity.
Credit risk is a different thing
The confusion that causes real damage: "safe" means two unrelated things in bonds.
Credit risk is whether you get repaid. Government bonds of a stable issuer have minimal credit risk. Junk bonds have a lot.
Duration risk is how much the price moves before repayment. It has nothing to do with creditworthiness.
A thirty-year government bond has essentially no credit risk and enormous duration risk. A one-year corporate bond from a shaky issuer has meaningful credit risk and almost no duration risk. Describing either as simply "safe" or "risky" hides which risk you are discussing, and investors who had internalised "government bonds are safe" were not wrong about credit — they were unaware of the other axis entirely.
Holding to maturity, and what a fund cannot do
A common reassurance: if you hold an individual bond to maturity, you get your face value back regardless of what happened to the price. True.
The nuance that gets skipped: you have still borne a cost. You are locked into a below-market rate for the remaining term. Your money is earning less than it could while newly issued bonds pay more. The loss did not appear on a statement; it appeared as forgone return, and it is real.
Bond funds work differently in a way that matters. A fund does not mature. It holds a rolling band of maturities — as bonds age out, new ones are bought. There is no date at which you are made whole.
That is not automatically worse. The fund is buying at the new higher rates, so its yield rises over time and eventually more than compensates, provided you hold roughly as long as the duration. The rough rule: hold a bond fund for at least its duration and a rate rise becomes approximately neutral, because the higher reinvestment income offsets the price fall.
What a fund cannot give you is a specific date with a specific amount. If you need £30,000 in exactly four years, an individual bond or a defined-maturity fund does that. A general bond fund does not, whatever its average maturity. See bond ladder strategy for building around specific dates.
Matching duration to need
The practical rule: match duration to when you need the money.
Money needed in a year belongs in something with duration measured in months. Money for a house deposit in five years belongs in short-to-intermediate bonds. Money for retirement in twenty-five years can tolerate long duration, and does not particularly need bonds at all at that horizon.
The failure mode is reaching for yield by extending duration. When long bonds pay more, buying them for a short-term need is taking a risk that is not compensated for the horizon you actually have — and when the curve is flat or inverted, you are extending duration for no additional yield at all, which is the worst version of the trade. The yield curve covers reading that relationship.
Common mistakes
- Conflating credit safety with price stability. Different risks entirely.
- Buying long bonds for short-term money. Uncompensated risk for your horizon.
- Panic-selling a bond fund after a rate rise. Locks in the loss and forfeits the higher reinvestment yield that repairs it.
- Ignoring duration on a fact sheet. It is the single most informative number there.
- Expecting a bond fund to mature. It never does.
- Assuming bonds always cushion equities. They can fall together when rates drive both.
- Extending duration for yield when the curve is flat. More risk, no more return.
FAQ
Where do I find a fund's duration?
On the fact sheet or fund page, usually as "effective duration" or "modified duration". If a fund does not disclose it prominently, that is itself worth noting.
Are short-duration bonds always safer?
Safer against rate moves, yes. They carry reinvestment risk instead — when they mature you reinvest at whatever rates then prevail, which may be lower. Every position on the curve trades one risk for another.
Does this apply to inflation-protected bonds?
They have duration too, measured against real rates rather than nominal ones. They protect against inflation, not against rate moves, and long-dated inflation-protected bonds can fall meaningfully when real rates rise.
What about individual bonds versus a fund?
Individual bonds give a maturity date and require you to manage a portfolio and accept less diversification. Funds give diversification and no maturity date. Defined-maturity ETFs are a middle path — see best index funds for the broader fund context.
Where to go next
For reading the rate environment duration reacts to, the yield curve. For building fixed income around specific dates, bond ladder strategy, and for why the order of returns matters in drawdown, sequence of returns risk.
This is general information, not investment advice. Nothing here accounts for your circumstances, horizon, or tax position.