Why Bond Prices Move

Executive Summary

It is a common source of confusion for newer fixed income investors: if a bond pays a fixed coupon, why does its price move at all? The answer lies in the fact that a bond's coupon is fixed, but the general level of interest rates, the market's assessment of the issuer's credit risk, and the passage of time toward maturity are all constantly shifting — and it is the interaction of these forces with a fixed coupon that produces price movement. This article explores, in general terms, the main drivers behind bond price fluctuations.

The Inverse Relationship with Interest Rates

The most fundamental driver of bond price movement is the general level of prevailing interest rates. Because a bond's coupon is fixed at issuance, changes in market interest rates alter the relative attractiveness of that fixed coupon. Consider a purely hypothetical bond with a 4% coupon, issued when comparable market yields were also around 4%. If market yields for similar bonds subsequently rise to 5%, our hypothetical bond's fixed 4% coupon becomes comparatively less attractive, and its price would generally need to fall so that a new buyer's yield to maturity is brought into line with the higher prevailing rate. Conversely, if market yields fell to 3%, the same bond's 4% coupon would look comparatively attractive, and its price would generally rise.

This inverse relationship between yields and prices is one of the most important concepts in fixed income investing, and it applies broadly across bond types, though the magnitude of price movement for any given change in yield depends heavily on the bond's duration, discussed further in our companion article on bond duration.

Credit Spreads and Issuer-Specific Risk

Beyond the general level of interest rates, a bond's price is also influenced by the market's assessment of the issuer's specific credit risk, generally expressed as a credit spread — the additional yield demanded over a comparable government benchmark bond. If market participants become more concerned about an issuer's financial position, whether due to company-specific developments or broader sector or economic conditions, credit spreads for that issuer's bonds may widen, meaning investors demand a higher yield to compensate for the perceived additional risk, which generally translates into a lower bond price, all else equal. Conversely, improving perceptions of creditworthiness can lead to spread narrowing and higher bond prices.

• Interest rate movements affect bond prices broadly across the market, largely irrespective of individual issuer.
• Credit spread movements are issuer- or sector-specific, reflecting changing perceptions of default risk.
• Time to maturity ('pull to par') causes bond prices to gradually converge toward face value as maturity approaches.
• Liquidity and trading volume can add additional price variability, particularly for smaller or less frequently traded bond issues.

A bond's coupon may be fixed, but its market price is a continuously updating verdict on interest rates, credit conditions and time.

The Pull to Par Effect

Regardless of how a bond's price has fluctuated during its life due to rate or credit spread movements, its price will generally converge toward its face value as it approaches maturity, assuming no default — a phenomenon often referred to as 'pull to par'. This occurs because, at maturity, the bond simply repays its face value, so any premium or discount embedded in the price must generally diminish as the maturity date nears. This is one reason why price volatility for a given bond generally tends to reduce as it moves closer to its maturity date, all else equal.

Key Considerations for Investors

• Recognise that bond price volatility does not necessarily indicate a change in the issuer's fundamental credit quality.
• Understand that if a bond is held to maturity and the issuer meets its obligations, interim price fluctuations may not affect the total return realised.
• Monitor both interest rate trends and issuer-specific credit developments, as they can move bond prices independently.
• Consider the general liquidity of a bond before assuming you can transact at a specific quoted price at any given time.
• Remember that Coyne Holdings' indicative Australian Fixed Rate Bond Index can offer a general reference point for broad market price trends.

Conclusion

Bond prices move in response to a combination of interest rate changes, shifting credit spreads, the passage of time toward maturity, and secondary market liquidity conditions. Understanding these drivers can help investors interpret price movements more calmly and avoid conflating short-term price volatility with a genuine change in an issuer's underlying capacity to meet its obligations. This article is general information only and does not constitute personal financial advice.

Related topics

Information contained within these insights is provided for general information purposes only and does not constitute personal financial advice, an offer or recommendation to acquire or dispose of any financial product. Investors should consider their individual circumstances and obtain appropriate professional advice before making investment decisions.