This spreadsheet was originally compiled to help make the decision to either sell mortgages that were originated, or keep them. It can also be used to help with the decision to purchase a pool of whole loans, or a securitized mortgage pools. Two different concepts of return are referred to in this post. The two are […]

# Category: Servicing

## Constant Default Rate (CDR)

Also see this post: Comparing CDR Default Formulas to Industry Standard Default Formulas Constant Default Rate (CDR) is an annualized rate of default on a pool of loans. The default rate on loans depends on a number of conditions, such as the age of the loans, seasonality, burnout levels, FICO, LTV, income, etc. Since […]

## Mortgage Pool Price and Average Life One Cell Formulas

See updated formula at: MBS Math Formula. Servicing, CPR, Payment Delay, Default Rate & Loss Severity http://pistulka.com/Other/?p=2384 A few posts back I showed the “megaformula” I used back in the day for calculating the price of a mortgage pool with prepayments (CPR). Rather than treating the one cell formula as just an interesting antique, I […]

## Mortgage Backed Securities (MBS) “MegaFormula”

See updated formula at: MBS Math Formula. Servicing, CPR, Payment Delay, Default Rate & Loss Severity http://pistulka.com/Other/?p=2384 This post is just to show you 20-somethings what we had to go through to calculate the price of a mortgage backed security back in the day. I had the first desktop computer (before Apple and Radio Shack were […]

## PSA vs. CPR

In past posts I showed you how to calculate a Constant Prepayment Rate (CPR) with an amortization schedule. This post will allow you to compare a CPR rate to a model provided by the Public Securities Association (PSA). PSA is based upon the CPR calculation. Both use a Single Monthly Mortality (SMM) calculation. The difference is […]

## Modified & Effective Duration, Plus Convexity of a Loan

The spreadsheet has been changed for this post. Please go to: Effective Duration, Convexity, and Convexity Adjustment For Loans My last post showed the formula to calculate a Macaulay Duration on an amortizing loan. The definition of a Macaulay Duration I used was “an effort to more accurately measure the term of an option-free fixed […]

## Macaulay Duration of an Amortizing Loan

The term “duration” is often used interchangeably by market participants to denote either a volatility measurement, a weighted term to maturity, or a portfolio risk measurement. In practice there is more than one definition of duration. The following describes the most basic duration along with it’s calculations. In a future posts we will discuss Modified Duration, Effective Duration, […]

## Valuing Servicing Matrix

On August 26, 2014 I showed an amortization schedule that could be used for initially valuing servicing. I introduced the use of constant prepayment rates (CPR) in order to get a more realistic pricing than assuming the pool of mortgages or commercial loans would never prepay. Considering the ease of refinancing and the mobility of the labor […]

## Valuing Servicing With CPR

Long before I wrote user defined functions for valuing servicing on a pool of mortgages, I developed amortization tables to understand the cash flows and proof my VBA. The amortization schedule provided below is not the typical amortization. It has a number of uses besides explaining the math of constant prepayment rates (CPR) and servicing. For example, if you […]