What it means
Many securities are built from a pool of loans, such as mortgages, car loans or credit card balances. As borrowers make payments and some repay early, the principal left in the pool shrinks.
The pool factor tracks this shrinkage in a single figure. A pool factor of 1.0 means nothing has been repaid.
A factor of 0.64 means 64% of the original principal is still outstanding and 36% has been paid down. Servicers or trustees publish the factor regularly, often monthly.
Investors use the factor to work out what their holding is currently worth in principal terms. Multiply the original face value of the investment by the latest pool factor and you have the current face value.
Interest is then paid on that smaller amount. The factor also gives clues about prepayment speed.
If the factor falls faster than the scheduled repayments alone would explain, borrowers are repaying early, which shortens the life of the security and changes its return. Investors who paid a premium for the security lose some of that premium when prepayments are fast.
The pool factor is not the same as credit quality. It describes how much has been repaid, not whether the remaining loans are performing, so it must be read together with default and delinquency data.
Reading the factor over time is more informative than reading a single figure. A steady monthly decline matches the scheduled repayment of the loans, while a sudden drop signals a burst of early repayments, perhaps caused by a fall in market interest rates.
Analysts compare the actual path with the path expected at issue to see how the pool is behaving.
In practice
Real-world examples.
Example
A bond fund manager receives the monthly report on a mortgage-backed security. The pool factor has dropped from 0.72 to 0.70, so the manager updates the fund's records of principal outstanding. It then reconciles the figure with the trustee's statement before the month-end close.
Example
A bank analyst studying a car-loan securitisation notices the factor falling faster than expected. The analyst concludes that borrowers are repaying early and revises the expected life of the security. The revised life changes the yield calculation for the holding.
Example
An insurer holding asset-backed securities reconciles its accounts with the trustee's report. It uses the pool factor to check that the principal balance in its ledger matches the trustee's figure. Any difference is raised with the trustee right away.
Formula
Calculation
Pool factor = current outstanding principal / original principal
Current face value of a holding = original face value x pool factor
Suppose a pool of mortgages originally had $100,000,000 of principal and now has $64,000,000 outstanding.
Pool factor = 64,000,000 / 100,000,000 = 0.64.
An investor who bought $5,000,000 of original face value now holds 5,000,000 x 0.64 = $3,200,000 of current face value.
Interest in the next period is calculated on $3,200,000, not on the original $5,000,000. At a 5% annual coupon, a year of interest on that holding is 3,200,000 x 0.05 = $160,000, against 5,000,000 x 0.05 = $250,000 if the factor were ignored.Case study
Seen in the real world.
Orchard Lane Financial is a fictional asset manager that holds $10,000,000 original face value of a mortgage-backed security. In this illustrative scenario, the pool factor is 0.90 at the end of year one. The manager's records show a current face value of 10,000,000 x 0.90 = $9,000,000.
A year later the factor is 0.78, much lower than the scheduled amortisation alone would explain, because interest rates have fallen and many homeowners have refinanced. The current face value is now 10,000,000 x 0.78 = $7,800,000, so $2,200,000 has been returned to the manager.
The manager recognises that faster repayment returns cash sooner than planned, and that reinvesting it will be at lower rates. The portfolio is adjusted to include securities with less prepayment risk, and the manager records the lesson for future purchases.
Watch out
Common mistakes.
- Using the original principal to calculate interest. Interest is based on the current balance, which is the original amount times the pool factor.
- Assuming a falling factor means trouble. It may simply mean borrowers are repaying as planned or early, which is a normal feature of loan pools.
- Reading the factor as a credit measure. It says nothing about whether the remaining loans are being paid on time, so delinquency and default reports must be read alongside it.
Questions
People also ask.
Can the pool factor go up?
Normally not, since principal only declines, unless more loans are added to the pool or an error is corrected.
How often is it published?
Usually monthly, by the servicer or trustee, and it is available to investors in the monthly remittance report.
Why do investors care about prepayments?
Early repayment shortens the security's life, returning principal sooner when reinvestment rates may be lower, which reduces the total interest earned.
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