The asset pool is divided into two ends, one end is the underlying assets (asset side), and the other end is the investors (securities side). The common mechanism is as follows: The cash flow generated by the underlying assets flows from the asset side into the securitized asset pool (cash inflow), and after being collected, it is paid to the investors on the securities side on the interest payment date (cash outflow).
For the convenience of description, we consider that within a natural year and 12 months, there are N delivery dates on the asset side, which are
- Given the annualized early repayment rate CPR, calculate the current early repayment amount
$C_i$ :
Assuming that the single-period early repayment rate
When the annualized early repayment rate is given, according to \eqref{SMM}\eqref{cpr}, we can calculate the early repayment amount
- Given the annualized default rate DR, calculate the current default amount
$D_i$ : Where$D_i$ is the default amount up to the i-th period,$X_{i-1}$ is the total outstanding amount at the beginning of the i-th period.
Given the annualized default rate DR,
Where
From the previous part, the total amount
- Tax
$Tax_i$ During the redemption process, a certain amount of tax will be incurred, which is 0.45% of$Sum_i$
- Interest on senior bonds
$I_{1,i}$
Given the ending balance
Where DATE is the interest accrual date of the bond.
- Interest on subordinated bonds
$I_{2,i}$
Before the principal of the senior bonds has been paid, the subordinated bonds will only pay interest, which is 2% of the total amount of the subordinated bonds.
- Pricing Based on Principal amount of senior bonds
$A_i$
At this point, the ending balance of the $i$th period on the securities side can be obtained
The cash flow
By Discounted Cash Flow Method, we can get:
so