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

A single payment of Rs 50,000 is due in exactly 7 years, and the valuation rate is 8% per annum effective. What is the discounted mean term (Macaulay duration) of this cashflow, in years?

The discounted mean term is 7.00 years. With a single payment, the PV-weighted average time is just the payment date, and the interest rate does not affect it. Dividing by 1.08 gives modified duration, not Macaulay duration.

  1. A7.56
  2. B6.48
  3. C3.50
  4. D7.00Correct
  5. 5.60

Explanation

The discounted mean term is the PV-weighted average of payment times. With one payment the weight is 1 at t = 7, so the DMT is 7.00 whatever the interest rate. The figure 6.48 is 7/1.08, which is the modified duration, not the Macaulay duration.

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