Bond duration — what it is and why it matters for Polish investors

Quick Answer

Duration measures a bond's price sensitivity to interest rate changes, expressed in years: if rates rise by 1 percentage point, the price falls by roughly the duration in percent (a duration of 5 means about -5%), and rises by the same amount if rates fall. Higher duration means greater price volatility, and duration rises with longer maturity, a lower coupon and a lower yield to maturity. Macaulay duration is the weighted-average time to receive cash flows, while modified duration estimates percentage price change directly. For bond ETFs it is a key parameter; if unsure, aim for duration ≤ 5. Educational information, not investment advice.

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What is duration?

Duration (time to maturity) is a measure of bond price sensitivity to interest rate changes. It's expressed in years and tells you: "if interest rates rise by 1 percentage point, bond price will fall by approximately X%", where X = duration.

Example

Bond with duration of 5:

• Interest rates rise by 1% → bond price falls by ~5%
• Interest rates fall by 1% → bond price rises by ~5%

The higher the duration, the greater the bond price volatility.

Types of duration

Macaulay Duration

Weighted average time to receive cash flows from the bond (coupons and principal). Expressed in years. For zero-coupon bonds = maturity date.

Modified Duration

Macaulay Duration divided by (1 + YTM/n). Directly measures percentage price change for a 1% interest rate change. This is the most commonly used measure in practice.

Effective Duration

Takes into account options embedded in the bond (e.g., call option). Used for complex bonds.

What affects duration?

A 10-year zero-coupon bond has duration = 10. A 10-year bond with 5% coupon has duration ~7–8.

Duration in bond ETFs

When choosing bond ETFs duration is a key parameter:

• Duration 1–3 → low volatility, low returns (short-term funds)
• Duration 5–7 → moderate volatility (medium-term funds)
• Duration 10+ → high volatility, interest rate speculation (long-term funds)

In rising interest rate environment → choose low duration. In falling rate environment → higher duration provides greater profit.

Practical rule

If you don't know what duration to choose — aim for duration ≤ 5. It's a good compromise between returns and risk for most investors.

How Freenance can help

Freenance helps track the bond portion of your portfolio — ETFs, Polish treasury bonds (SPW), and money market funds. You'll see how different instruments affect overall portfolio risk and returns.

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FAQ

What is bond duration in plain English?

Duration is a measure of how sensitive a bond's price is to changes in interest rates, expressed in years. As a rough rule, a bond with duration of 5 will lose about 5% of its market value if interest rates rise by 1 percentage point, and gain a similar amount if they fall by 1 point. The higher the duration, the more the price moves for the same rate change.

What is the difference between Macaulay and modified duration?

Macaulay duration is the weighted average time until you receive all the bond's cash flows (coupons plus principal), expressed in years. Modified duration takes Macaulay duration and divides it by (1 + yield/n), which converts it into a direct estimate of percentage price change per 1% move in yield. In practice, traders and ETF factsheets most often quote modified duration.

Why does a higher coupon mean lower duration?

A higher coupon returns more cash to you earlier in the bond's life, shifting the weighted-average timing of cash flows closer to today. That shorter effective wait reduces sensitivity to interest-rate changes. Zero-coupon bonds have the highest duration for a given maturity because all the cash flow comes at the very end.

How does duration affect bond ETFs?

Bond ETFs publish an average duration for the whole basket of bonds they hold. Short-duration ETFs (1–3 years) move relatively little when rates change, while long-duration ETFs (10+ years) can swing sharply. Choosing duration that matches your time horizon and rate outlook is one of the key decisions when adding bond ETFs to a portfolio.

Does duration apply to Polish retail treasury bonds (SPW)?

Duration is a market-price concept, so it matters most for bonds you trade on the secondary market or hold via ETFs. Polish retail savings bonds (such as ROR, DOR, COI, EDO) are typically held to maturity at fixed redemption rules, so day-to-day rate moves do not directly hit your account value. This is general information and not investment advice — check the prospectus or speak with a qualified adviser before deciding.