YTM and Modified Duration: Reading a Debt Fund Fact Sheet

Equity funds are judged on things like standard deviation and Sharpe ratio, as our page on Sharpe ratio and standard deviation explains.

Debt funds are different. They hold bonds and similar instruments, which pay interest and mature on set dates. What matters most for them is how much the holdings are yielding and how sensitive they are to interest rates. That is what YTM and duration measure. Our page on debt funds explains the basics.

Yield to maturity, or YTM, is the annual yield the fund current portfolio would earn if every bond were held until it matures and every payment came in as expected.

Think of it as a snapshot of what the holdings are earning today, based on their current prices. It is shown before the fund expenses are deducted.

Many people see a YTM figure and assume that is what they will earn. It is not.

The fund does not hold everything to maturity. It buys and sells, and new money comes in at different yields. Interest rates change, which changes bond prices. And the fund charges expenses, which come off the top. So your actual return can be higher or lower than the YTM shown today.

Use YTM as a rough guide to what the portfolio is earning now, not as a promise. Our page on expense ratio explains the cost side.

Average maturity is the average time left until the bonds in the portfolio mature. A liquid fund might have an average maturity of weeks. A long duration fund might have years.

It gives a quick sense of whether the fund is short-term or long-term. But duration, explained next, is the more precise measure of rate sensitivity.

Modified duration tells you roughly how much a fund value will move for a given change in interest rates.

A simple way to read it: if modified duration is, say, three, the fund value might move by roughly three percent in the opposite direction for a one percentage point change in rates. Rates up, value down. Rates down, value up.

So a higher number means more sensitivity. A fund with a modified duration of six will swing roughly twice as much as one with three, for the same rate move.

Macaulay duration is a related measure. It is the weighted average time until the fund receives its cash flows, meaning interest and principal.

For everyday investors, modified duration is the more useful one, because it links directly to how much the value moves with rates. You can mostly ignore Macaulay duration unless you are comparing technical details.

If you hold a bond paying a fixed interest, and new bonds start paying more, your older bond becomes less attractive. Its price falls until its yield matches the new level.

The longer the bond has left, the more its price has to move. That is why long duration funds swing more when rates change. Our page on medium and long duration funds explains this in more detail.

A high YTM can be a warning sign as well as an attraction. Bonds from weaker borrowers pay higher yields because there is more risk they will not pay back.

So always check the credit rating breakdown on the fact sheet alongside YTM. A fund with an unusually high YTM for its category may be holding lower-rated paper. Our page on credit risk funds explains this risk.

A useful rule of thumb: pick a debt fund whose duration is not much longer than your own holding period.

Money needed in a few months suits very short duration funds such as liquid or ultra-short funds. Money needed in two or three years might suit short duration funds. Only long-term money should go into long duration funds.

Because YTM is shown before expenses, a rough way to think about what the portfolio is earning for you is YTM minus the expense ratio. This is only an approximation, and it still assumes nothing changes, which never happens exactly.

It is most useful for comparing two similar funds side by side, not for predicting your return.

Every debt fund monthly fact sheet shows YTM, modified duration, Macaulay duration and average maturity, usually in a small portfolio statistics box. Our page on the fact sheet explains where to look.

The numbers change every month as the portfolio changes, so check the latest one rather than an old copy.

• Compare funds only within the same category.
• Look at YTM and credit quality together.
• Check modified duration to understand rate sensitivity.
• Compare expense ratios, which matter a lot in debt funds.

A slightly lower YTM with better credit quality and lower costs is often the more sensible choice.

• YTM: what the portfolio is yielding now, before costs. Not a promise.
• Modified duration: how much the value moves when rates change.
• Average maturity: roughly how long the holdings last.
• Credit quality: always check it next to YTM.

We are distributors rather than investment advisers and we recommend no schemes. If you want help reading a debt fund fact sheet, get in touch.