Dear All:

According to the problem below, why 100 SPA = 0.2%, Could you please explain something about the SPA.

thank you so much for your time

The SMM formula is: SMM = 1 – (1 – CPR)^{1/12}. Calculate the single monthly mortality rate (SMM) for month 6, 100 PSA:

**A)** 0.000837. **B)** 0.001259. **C)** 0.001006.

**Your answer: C was correct!**

CPR = 0.2% * 6 = 0.012

SMM = 1-(1-0.012)^{1/12} = 0.001006