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IAI Actuarial Core Principles · Actuarial Mathematics for Modelling · Duration, convexity and immunisation

A bond portfolio has a Macaulay duration of 6.6 years at an effective annual yield of 10%. Using the duration approximation, by roughly what percentage does its value fall if the yield rises immediately by 0.5 percentage points?

The value falls by about 3.00%. Modified duration is Macaulay duration divided by 1.10, which equals 6.00. Multiplying by the yield rise of 0.005 gives a 3.00% fall. Using 6.6 directly would wrongly give 3.30%.

  1. A3.30%
  2. B3.00%Correct
  3. C3.50%
  4. D6.00%
  5. 2.75%

Explanation

Modified duration = 6.6/1.10 = 6.00. The approximate percentage change in value is −6.00 × 0.005 = −3.00%. Using the Macaulay duration directly would give 3.30%, which forgets to divide by (1+i).

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