Pool factor

Key takeaways

Pool factor belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pool factor to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pool factor from memory before moving on to harder problems.

Reference excerpt

In finance, a pool factor is the amount of the initial principal of the underlying mortgage loans that remain in a mortgage-backed security transaction. It is expressed as a factor of one that is used to indicate the remaining principal balance. Pool factors are only used to describe specific classes of securities, namely pooled asset-backed securities (ABSs) and mortgage-backed securities (MBSs) whose component payments are returned to investors on a monthly basis. Pool factors are published monthly in the US for Ginnie Mae, Fannie Mae, and Freddie Mac mortgage-backed securities.

Calculation To calculate the pool factor,

O u t s t a n d i n g P r i n c i p a l B a l a n c e O r i g i n a l P r i n c i p a l B a l a n c e = P o o l F a c t o r {\displaystyle {OutstandingPrincipalBalance \over OriginalPrincipalBalance}={PoolFactor}}

For example, a pool factor of 0.523 indicates that for each note of $10,000, $4,770 of principal has been repaid. If one multiplies the original face value of mortgage back security with the pool factor, we get the current face value.

Usage Asset-backed securities and MBSs typically contain issue terms that specify a method through which redeeming principal is shared among investors. When redemption is done pro-rata, a pool factor is useful to investors in cases of early repayment. Early repayment reduces the amount of collateral available for an issue, and therefore some of the outstanding principal is returned to investors as stated in the issue terms. In this case, the pool factor is used to indicate how the remaining outstanding principal is adequately securitized.

References

Worked examples

Example 1 — a first encounter with Pool factor

Start with the simplest possible case. Write down what Pool factor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pool factor before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pool factor ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pool factor

In research: Pool factor appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pool factor in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pool factor is common in secondary-school and first-year university syllabi. It links to neighbouring topics Finance stubs, Fixed income, so understanding it makes those chapters shorter.
In everyday life: Look for Pool factor outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Pool factor in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pool factor means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pool factor out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pool factor in simple terms?

In finance, a pool factor is the amount of the initial principal of the underlying mortgage loans that remain in a mortgage-backed security transaction. It is expressed as a factor of one that is used to indicate the remaining principal balance.

Why does Pool factor matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pool factor?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pool factor.