这道题不理解：
为什么Type1可以用 duration match-BPV ，其他type不可以用BPV吗？
36. Who is least likely correct with regard to the measures that clients in Exhibit 1 use when immunizing their liabilities?
A. Shrewsbury regarding Type I investors
B. Silver regarding Type I, II, III, and IV investors
C. Shrewsbury regarding Type II, III, and IV investors
Silver tells Shrewsbury, “Managing fixed-income portfolios to meet obligations requires an understanding of the nature of the liabilities. Clients with liability types such as those listed in Exhibit 1 use yield statistics, such as Macaulay, modified duration, money durations, and the present value of a basis point (PVBP), when implementing immunization strategies.”
Shrewsbury responds, “Only Type I clients can measure the interest rate sensitivity of liabilities using yield statistics. Those with Type II, III, and IV liabilities must use a curve duration statistic, such as effective duration, to estimate interest rate sensitivity.”
B is correct. Silver is correct in that Type I clients can use a yield statistic for immunizing their liabilities, but he is incorrect in stating that Type II, III, and IV investors can use the same approach. An advantage to knowing the size and timing of cash flows is that yield duration statistics—that is, Macaulay duration, modified duration, money duration, and PVBP—can be used to measure the interest rate sensitivity of the liabilities. With Type II, III, and IV liabilities, a curve duration statistic known as effective duration is needed to estimate interest rate sensitivity. This statistic is calculated using a model for the uncertain amount and/or timing of the cash flows and an initial assumption about the yield curve.
