What does cpr stand for ?

The conditional prepayment rate refers to the annualized percentage of the pre-existing mortgage pool that is expected to be prepaid in the year. It is the percentage of the outstanding amount of the security or the loan minus the scheduled payments.   

It is assumed the prepayment rate will be constant when a constant percentage of the mortgage is given. The factor CPR depends on factors like the underlying pool, future predictions and the historical prepayment rate. 

It is used for various loans like mortgages, student loans, and pass-through securities. It is mostly expressed as a percentage.