Original practice · fully worked
Original variant: estimated gain on an immediate perpetuity
A level perpetuity-immediate pays 500 annually and is valued at 6% effective. The yield immediately falls to 5%. Using first-order modified duration, estimate the dollar increase in value.
- A
833.33 - B
1,000.00 - C
1,250.00 - D
1,388.89 - E
1,666.67
Answer and calculation
The initial price is 8333.33 and modified duration is 16.6667. A one-percentage-point decline produces an estimated gain of 1388.89, choice D.
Setup
Setup
Price the immediate perpetuity and compute its modified duration.
P0=0.06500=8,333.333 Dmod=0.061=16.666667 Model
Model
The yield change is negative 0.01.
Δi=0.05−0.06=−0.01 Compute
Compute
Apply the first-order relative price change and convert it to dollars.
ΔP≈−P0DmodΔi ΔP=1,388.889 Answer
Answer
The estimated gain is 1388.89, choice D.
ΔP≈1,388.89(D)