Bond Fund Duration Risk: Why a Unit Trust Bond Fund Can Still Lose Value

Rates moved, not the bonds themselves

A bond pays a fixed coupon. If you bought a bond paying 4% and new bonds now come out paying 5%, nobody wants your 4% bond at the price you paid for it. Its market value falls until its effective yield looks competitive again. That happens whether or not the issuer is in perfect financial health.

A bond fund holds a basket of these bonds and marks them to current market value every day. So when rates move up across the board, the fund's unit price falls, even though every bond inside it may still be paying its coupon exactly on schedule. The fund has not lost money in the sense of a default. It has lost value in the sense that the bonds it holds are now worth less to someone buying today.

Duration is the number that tells you how much

Duration is a measure, roughly in years, of how sensitive a bond or bond fund is to a change in interest rates. As a rule of thumb, if a fund has a duration of 5 years, a 1 percentage point rise in interest rates would be expected to reduce the fund's value by roughly 5%. A fund with a duration of 10 years would be expected to fall by roughly 10% for the same rate move.

Longer-tenure bonds carry higher duration because their fixed coupon is locked in for longer, so a rate change affects a longer stream of future payments. A fund holding mostly short-tenure bonds, or Malaysian government securities close to maturity, will usually swing far less than a fund built around long-dated bonds.

Check the fund fact sheet for the stated modified duration before assuming a bond fund is automatically low-risk. Two funds both labelled "bond fund" can behave very differently in the same rate environment.

This works the other way too

The same relationship applies when rates fall. A fund with a longer duration gains more value when interest rates come down, because its locked-in higher coupon becomes more attractive relative to new bonds. That is why some bond funds had a strong run in periods when rates were cut, and why the same fund can then give some of that back once rates hold steady or rise again.

None of this means the fund manager did something wrong. Duration risk is built into how bonds are priced. The fund did what a bond fund does.

Duration risk is not the same as credit risk

A bond fund can also lose value because an issuer actually cannot pay, misses a coupon, or gets downgraded. That is credit risk, and it behaves differently: it usually hits a specific bond or a specific sector, not the whole fund uniformly, and it does not reverse just because rates move the other way.

If your bond fund's value drops, the useful question is which one happened. A broad, sudden move across most bond funds after an interest-rate announcement points to duration. A drop concentrated in one fund, or tied to news about a specific issuer, points to credit. The fund's monthly or quarterly commentary usually says which.