Original practice · fully worked
Original variant: comparing two duration estimates for a housing note
A housing note is worth 10,000 at 5% yield and has modified duration 4. Yield rises to 6%. Let M be the Macaulay-ratio estimate and L the modified-duration linear estimate. Calculate M − L.
- A
−20.00 - B
0.00 - C
9.71 - D
20.00 - E
40.00
Answer and calculation
Macaulay duration 4.2 gives M = 9,609.71 while L = 9,600; the difference is 9.71, choice C.
Setup
Setup
The ratio approximation requires Macaulay duration, obtained by multiplying the given modified duration by 1.05.
DM=4(1.05)=4.2 Model
Model
Evaluate both estimates at the same one-point increase before comparing them.
M=10000(1.05/1.06)4.2=9609.7131 Compute
Compute
The ratio method gives 9,609.7131 and the linear method gives 9,600.
L=10000[1−4(0.01)]=9600 Answer
Answer
Their difference is 9.71, so choice C is correct.
M−L=9.71(C)