Final - Interest Rate Sensitivity and Duration in Fixed Income

KELLEY SCHOOL OF BUSINESS

F303 - Intermediate Investments

Professor Mathias S. Kruttli

Spring 2026

11 - Fixed Income III: Interest Rate Sensitivity

Agenda
  • Interest rate sensitivity

  • Concept of duration

  • Calculating durations

  • Approximating bond price changes with duration

Bond Price Interest Rate Sensitivity
  • The percentage change in bond price is inversely related to changes in yield to maturity.

  • Quantitative Representation:   - extPercentageChangeinBondPriceextextChangeinYieldtoMaturityext{Percentage Change in Bond Price} ext{ ∝ } ext{Change in Yield to Maturity}

Maturity Sensitivity
  • Long-term vs. Short-term Bonds:   - Long-term bonds tend to exhibit greater sensitivity to interest rate changes compared to short-term bonds.

Coupon Sensitivity
  • High-Coupon vs. Low-Coupon Bonds:   - Prices of high-coupon bonds are less sensitive to interest rate changes than those of low-coupon bonds.

Coupon Rate and Interest Rate Sensitivity
  • Example 1: Prices of an 8% coupon bond (with semi-annual payments) affected by YTM.   -     | YTM | T = 1 | T = 10 | T = 20 |     |-------|-------|--------|--------|     | 8% | $1,000| $1,000 | $1,000 |     | 9% | $990.64| $934.96| $907.99|     | Price Change (%) | 0.94% | 6.50% | 9.20% |

  • Example 2: Prices of zero-coupon bonds (with semi-annual compounding).   -     | YTM | T = 1 | T = 10 | T = 20 |     |-------|--------|---------|---------|     | 8% | $924.56| $456.39 | $208.29 |     | 9% | $915.73| $414.64 | $171.93 |     | Price Change (%) | 0.96% | 9.15% | 17.46% |   - Conclusion: The zero-coupon bond demonstrates longer duration and more pronounced price changes when yield shifts from 8% to 9%.

Yield to Maturity Sensitivity
  • High-YTM vs. Low-YTM Bonds:   - Prices of low-YTM bonds show greater sensitivity to interest rate changes than those of high-YTM bonds.

Duration Concept
  • Definition of Duration:   - Duration measures the average time to receive the bond's promised cash flows. It provides a metric for how sensitive a bond is to interest rate changes—greater duration equates to higher sensitivity.

  • Macaulay Duration Equation:   - For a bond with cash flows, where yy is the yield to maturity:   - P=racC(1+y)+racC(1+y)2++racC+F(1+y)nP = rac{C}{(1+y)} + rac{C}{(1+y)^2} + … + rac{C+F}{(1+y)^n}   - Macaulay's Duration is computed as:   - D=racextTotalCashFlowWeightPD = rac{ ext{Total Cash Flow Weight}}{P}, where:   - wt=racCFt(1+y)tw_t = rac{CF_t}{(1+y)^t} for cash flows at time tt.

Duration: Calculation Examples
  • Example 1: Determining duration for a 10-year zero-coupon bond priced at $500 with a YTM of 3.526% (semi-annual).

  • Example 2: Duration for an 18-month bond with an 8% coupon rate, semi-annual payments, BEY of 10%, face value of $1,000.

  • Example 3: Macaulay’s duration for a 2-year bond with a 4% semiannual coupon and face amount of $2,000, BEY of 2.5%.

Estimating Bond Price Changes with Duration
  • Approximation Formula:
      - The bond's percentage price change can be estimated using:   - racrianglePPextapprox.Dimesracriangley(1+y)rac{ riangle P}{P} ext{ approx. } -D imes rac{ riangle y}{(1+y)}   - Modified Duration Definition:
      - D=racD(1+y)D^* = rac{D}{(1+y)}

Duration Approximation Accuracy
  • Graphical Representation:
      - Comparison of Duration Approximation vs. Actual Change:   - Actual price changes are not perfectly predicted by duration approximation.   - Accuracy diminishes with larger changes in interest rates.

Duration: Example Calculations
  • Example 4 Calculation:
      - If the YTM changes from 5% to 6% for the 18-month bond (BEY of 10%, coupon rate of 8%, face value of $1,000, initial price of $972.77):   - Approximate percentage change in price calculated as:   - racrianglePP=Dimesriangley=2.74ext(forriangley=0.01ext)rac{ riangle P}{P} = -D imes riangle y = -2.74 ext{ (for } riangle y = 0.01 ext{)}

Summary of Duration Metrics
  1. The duration of a zero-coupon bond is equivalent to its maturity.

  2. For constant maturity and YTM, a bond's duration increases with a lower coupon rate.

  3. For a constant coupon rate, duration and interest rate sensitivity generally increase with longer maturities.

  4. For consistent factors, a bond's duration is higher with a lower YTM.

Quick Quiz: Duration Consideration
  • If all else being equal, does a higher coupon payment lead to lower duration?
      - A. Yes
      - B. No
      - C. Not enough information

Quiz Example Calculation
  • Find the Macaulay’s duration of a 2-year bond with a semiannual coupon rate of 6%, face amount of $1,000, and BEY of 10%:   - Possible options:   - A. 3.82
      - B. 1.21
      - C. 2.74

Modified Duration Portfolio Example
  • A bond portfolio has a modified duration of 5 years. If the annual yield for all bonds decreases by 2%, the approximate percentage change in portfolio value can be estimated as:   - A. 2%
      - B. 10%
      - C. 15%

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