paid in full, regardless of prepayment). In general, only borrowers who expect to keep their loans for many years should opt for below-market interest rates by paying mortgage origination points or forgoing automobile rebates. Homeowner prepayment decisions are impacted by a number of variables and are notoriously hard to predict, adding another layer of uncertainty to investing in MBS markets. Prepayment speeds can be expressed in SMM (Single Monthly Mortality), CPR (Conditional Prepayment Rate, which is the annually compounded SMM), or PSA (percentage of the Public Securities Association prepayment model). For mortgages at least 30 months old, 100% PSA = 6.0% CPR = 0.51% SMM, equivalent to the full prepayment of 6% of a pool's remaining mortgages each year. References Structured finance Loans