Original practice · fully worked
Original variant: select a locally immunizing asset portfolio
A liability portfolio has present value 1,000, modified duration 6.0, and convexity 50. Which candidate asset portfolio satisfies the local value, duration, and curvature conditions for immunization?
- A
PV 1,000; modified duration 5.5; convexity 55 - B
PV 980; modified duration 6.0; convexity 55 - C
PV 1,000; modified duration 6.0; convexity 55 - D
PV 1,000; modified duration 6.0; convexity 45 - E
PV 1,020; modified duration 6.5; convexity 60
Answer and calculation
Only candidate C matches value and modified duration while retaining greater convexity, so choice C is correct.
Setup
Setup
Test each candidate first for value equality, because a value mismatch leaves an immediate surplus or deficit.
PA=PL=1000 Model
Model
Next require equal modified duration so that the first-order response to a small rate change cancels.
DAmod=DLmod=6.0 Compute
Compute
Candidate C also has convexity above 50, making the local second-order surplus positive.
CA=55>50=CL Answer
Answer
Candidate C is the only locally immunizing portfolio.
Candidate C satisfies all three conditions