Bond Volatility, Duration, and Reinvestment Risk

Bond volatility is the practical side of the price-yield relationship. Once students understand that yields and prices move inversely, the next question is how much a bond is likely to move. WME questions often test which bond is more interest-rate sensitive and whether price risk or reinvestment risk is the more important concern in the case.

Why Some Bonds Move More Than Others

Two broad factors strongly affect bond price sensitivity:

• maturity
• coupon level

In general:

• longer-maturity bonds react more to yield changes than shorter-maturity bonds
• lower-coupon bonds react more to yield changes than higher-coupon bonds

The intuition is simple. When more of the bond’s value depends on cash flows arriving far in the future, changes in the discount rate matter more.

Duration as a Conceptual Measure

Duration is a measure of interest-rate sensitivity. For WME purposes, students should think of it as a summary indicator of how strongly a bond price is likely to react to a change in yield.

At a high level, the approximate relationship is:

Where:

• \%\Delta P is the approximate percentage price change
• D is duration
• \Delta y is the change in yield

The negative sign reflects the inverse relationship between price and yield.

Students do not need advanced duration mathematics for most WME questions. They do need to recognize that:

• higher duration means more price sensitivity
• lower duration means less price sensitivity

Price Risk Versus Reinvestment Risk

Fixed-income planning involves a tradeoff between:

• price risk, the risk that bond prices change because yields move
• reinvestment risk, the risk that coupons or maturing proceeds must be reinvested at less favorable rates

These risks do not dominate equally in every situation.

Shorter-term and higher-coupon structures often reduce price risk but can increase reinvestment dependence, because more cash must be reinvested sooner. Longer-term and lower-coupon structures often reduce reinvestment pressure but increase price sensitivity.

When Reinvestment Risk Becomes the Main Issue

Reinvestment risk matters more when:

• the client depends on ongoing coupon income
• rates may fall
• cash flows arrive sooner and more frequently

This is why a high-coupon bond can still create a planning problem in a falling-rate environment even if its market price is relatively stable.

When Price Volatility Becomes the Main Issue

Price volatility matters more when:

• the client may need to sell before maturity
• the investment horizon is short
• the bond has long duration
• the portfolio is meant to provide stability rather than tactical rate exposure

In these cases, students should be cautious about recommending long-term low-coupon debt simply because the headline yield looks attractive.

Example

A client will likely spend the capital in three years. Another bond offers a slightly higher yield, but it has a much longer maturity and materially higher duration. Even if the client likes the extra income, the more important issue may be price risk, because the client may have to sell before maturity.

Sample Exam Question

A client may need to sell a fixed-income holding in three years. One option has slightly higher yield but much longer duration. What is the strongest concern?

• A. The longer-duration bond may expose the client to more price risk than the short horizon supports.
• B. Higher yield always eliminates interest-rate sensitivity.
• C. Duration matters only for equities.
• D. Reinvestment risk is the only risk in all bond cases.

Correct answer: A

Explanation: If the client may sell before maturity, market-value volatility matters. A small yield advantage may not justify materially higher duration risk.

Common Pitfalls

• assuming all bonds with the same credit quality have similar volatility
• ignoring maturity when comparing fixed-income options
• overlooking coupon level as a driver of duration
• treating reinvestment risk and price risk as the same thing
• choosing the highest yield without asking which risk is being increased

Key Takeaways

• Longer maturity usually means greater price volatility.
• Lower coupon usually means greater price volatility.
• Duration is a conceptual measure of interest-rate sensitivity.
• Price risk and reinvestment risk are different and often move in opposite directions.
• In WME questions, the correct bond choice often depends on which of those risks matters more to the client.

Quiz