Original practice · fully worked
Original variant: missing curvature condition in a proposed immunization program
At a reference yield, an insurer's asset value equals its liability value and the two modified durations coincide, but asset convexity is lower than liability convexity. Which conclusion is correct about Redington immunization?
- A
The position is Redington immunized because value matching alone is sufficient. - B
The position is Redington immunized because duration matching alone is sufficient. - C
The position is fully cash-flow matched. - D
The position is not Redington immunized because the convexity inequality has the wrong direction. - E
The position is protected against every possible yield change.
Answer and calculation
Value and duration matching remove the constant and first-order mismatch, but lower asset convexity makes the second-order surplus term unfavorable. The position is not Redington immunized, so choice D is correct.
Setup
Setup
The proposed position satisfies the value and first-order sensitivity conditions.
A(i0)=L(i0) DA(i0)=DL(i0) Model
Model
Redington immunization additionally requires asset convexity to exceed liability convexity.
CA(i0)>CL(i0) Compute
Compute
Here the supplied inequality is reversed, so the local second-order surplus condition fails.
CA(i0)−CL(i0)<0 Answer
Answer
The position is not Redington immunized for the stated reason, selecting choice D.
not Redington immunized(D)