Mortgage-Backed Securities

Products, Structuring, and Analytical Techniques

Frank J. Fabozzi, Anand K. Bhattacharya, William S. Berliner

• Publisher: Wiley
• Year: 2010
• Print ISBN: 9780470047736
• eBook ISBN: 9781118044711
• Edition: 1
• Topic: Business
• Subtopic: Real Estate
• Index: Business

An in-depth look at the latest innovations in mortgage-backed securities

The largest sector of the fixed-income market is the mortgage market. Understanding this market is critical for portfolio managers, as well as issuers who must be familiar with how these securities are structured. Mortgage-Backed Securities is a timely guide to the investment characteristics, creation, and analysis of residential real estate-backed securities. Each chapter contains cutting-edge information for investors, traders, and other professionals involved in this market, including discussions of structuring mortgage products-such as agency CMOs and new types of mortgages-and an in-depth explanation of the concept of option-adjusted spreads and other analytical concepts used to assess relative value.

PART One

Introduction to Mortgage and MBS Markets

CHAPTER 1

Overview of Mortgages and the Consumer Mortgage Market

The mortgage market in the United States has emerged as one of the world’s largest asset classes. According to Federal Reserve statistics, the total face value of 1-4 family residential mortgage debt outstanding was approximately $9.5 trillion as of the third quarter of 2006. The growth of the mortgage market is attributable to a variety of factors. Most notably, strong sales and price growth in the domestic real estate markets and the increased acceptance of new loan products on the part of the consumer has dovetailed with increased comfort levels with respect to the credit quality of the sector and the acceptance of a variety of loan products as collateral for securitizations.

Due to a variety of reasons such as product innovation, technological advancement, and demographic and cultural changes, the composition of the primary mortgage market is evolving at a rapid rate—older concepts are being updated, while a host of new products is also being developed and marketed. Consequently, the mortgage-lending paradigm continues to be refined in ways that have allowed lenders to offer a large variety of products designed to appeal to consumer needs and tastes. This evolution has been facilitated by sophistication in pricing that has allowed for the quantification of the inherent risks in such loans. At the same time, structures and techniques that allow the burgeoning variety of products to be securitized have been created and marketed, helping to meet the investment needs of a variety of market segments and investor clienteles.

The purpose of this chapter is to explain mortgage products and lending practices. The chapter introduces the basic tenets of the primary mortgage market and mortgage lending, and summarizes the various product offerings in the sector. In conjunction with the following chapter on mortgage-backed securities (MBS) and the MBS market, this chapter also provides a framework for understanding the concepts and practices addressed in the remainder of this book.

OVERVIEW OF MORTGAGES

In general, a mortgage is a loan that is secured by underlying assets that can be repossessed in the event of default. For the purposes of this book, a mortgage is defined as a loan made to the owner of a 1-4 family residential dwelling and secured by the underlying property (both the land and the structure or “improvement”). After issuance, loans must be managed (or serviced) by units that, for a fee, collect payments from borrowers and pass them on to investors. Servicers are also responsible for interfacing with borrowers if they become delinquent on their payments, and also manage the disposition of the loan and the underlying property if the loan goes into foreclosure.

Key Attributes that Define Mortgages

There are a number of key attributes that define the instruments in question that can be characterized by the following dimensions:

• Lien status, original loan term

• Credit classification

• Interest rate type

• Amortization type

• Credit guarantees

• Loan balances

• Prepayments and prepayment penalties

We discuss each below.

Lien Status

The lien status dictates the loan’s seniority in the event of the forced liquidation of the property due to default by the obligor. A first lien implies that a creditor would have first call on the proceeds of the liquidation of the property if it were to be repossessed. Borrowers often utilize second lien or junior loans as a means of liquefying the value of a home for the purpose of expenditures such as medical bills or college tuition or investments such as home improvements.

Original Loan Term

The great majority of mortgages are originated with a 30-year original term. Loans with shorter stated terms are also utilized by those borrowers seeking to amortize their loans faster and build equity in their homes more quickly. The 15-year mortgage is the most common short-amortization instrument, although issuance of loans with 20- and 10-year terms has grown in recent years.

Credit Classification

The majority of loans originated are of high-credit quality, where the borrowers have strong employment and credit histories, income sufficient to pay the loans without compromising their creditworthiness, and substantial equity in the underlying property. These loans are broadly classified as prime loans, and have historically experienced low incidences of delinquency and default.

Loans of lower initial credit quality which are more likely to experience significantly higher levels of default, are classified as subprime loans. Subprime loan underwriting often utilizes nontraditional measures to assess credit risk, as these borrowers often have lower income levels, fewer assets, and blemished credit histories. After issuance, these loans must also be serviced by special units designed to closely monitor the payments of subprime borrowers. In the event that subprime borrowers become delinquent, the servicers move immediately to either assist the borrowers in becoming current or mitigate the potential for losses resulting from loan defaults.

Between the prime and subprime sector is a somewhat nebulous category referenced as alternative-A loans or, more commonly, alt-A loans. These loans are considered to be prime loans (the “A” refers to the A grade assigned by underwriting systems), albeit with some attributes that either increase their perceived credit riskiness or cause them to be difficult to categorize and evaluate.

Mortgage credit analysis employs a number of different metrics, including the following.

Credit Scores Several firms collect data on the payment histories of individuals from lending institutions and use sophisticated models to evaluate and quantify individual creditworthiness. The process results in a credit score, which is essentially a numerical grade of the credit history of the borrower. There are three different credit-reporting firms that calculate credit scores: Experian (which uses the Fair Isaacs or FICO model), Transunion (which supports the Emperica model), and Equifax (whose model is known as Beacon). While each firm’s credit scores are based on different data sets and scoring algorithms, the scores are generically referred to as FICO scores.

Loan-to-Value Ratios The loan-to-value ratio (LTV) is an indicator of borrower leverage at the point when the loan application is filed. The LTV calculation compares the face value of the desired loan to the market value of the property. By definition, the LTV of the loan in the purchase transaction is a function of both the down payment and the purchase price of the property. In a refinancing, the LTV is dependent upon the requested amount of the new loan and the market value of the property as determined by an appraisal. If the new loan is larger than the original loan, the transaction is referred to as a cash-out refinancing, while a refinancing where the loan balance remains unchanged is described as a rate-and-term refinancing or no-cash refinancing.

The LTV is important for a number of reasons. First, it is an indicator of the amount that can be recovered from a loan in the event of a default, especially if the value of the property declines. The level of the LTV also has an impact on the expected payment performance of the obligor, as high LTVs indicate a greater likelihood of default on the loan. Another useful measure is the Combined LTV (or CLTV), which accounts for the existence of second liens. A $100,000 property with an $80,000 first lien and a $10,000 second lien will have an LTV of 80% but a CLTV of 90%.

Income Ratios In order to ensure that borrower obligations are consistent with their income, lenders calculate income ratios that compare the potential monthly payment on the loan to the applicant’s monthly income. The most common measures are called front and back ratios. The front ratio is calculated by dividing the total monthly payments on the home (including principal, interest, property taxes, and homeowners insurance) by pretax monthly income. The back ratio is similar, but adds other debt payments (including auto loan and credit card payments) to the total payments. In order for a loan to be classified as prime, the front and back ratios should be no more than 28% and 36%, respectively. (Because consumer debt figures can be somewhat inconsistent and nebulous, the front ratio is generally considered the more reliable measure, and accorded greater weight by underwriters.)

Documentation Lenders traditionally have required potential borrowers to provide data on their financial status, and support the data with documentation. Loan officers typically required applicants to report and document income, employment status, and financial resources (including the source of the down payment for the transaction). Part of the application process routinely involved compiling documents such as tax returns and bank statements for use in the underwriting process. However, a growing number of loan programs have more flexible documentation requirements, and lenders typically offer programs with a variety of documentation standards. Such programs include programs where pay stubs and tax returns are not required (especially in cases where existing customers refinance their loans), as well as “stated” programs (where income levels and asset values are provided, but not independently verified).

Characterizing Prime versus Subprime Loans

The primary attribute used to characterize loans as either prime or subprime is the credit score. Prime (or A-grade) loans generally have FICO scores of 660 or higher, income ratios with the previously noted maximum of 28% and 36%, and LTVs less than 95%. Alt-A loans may vary in a number of important ways. Alt-A loans typically have lower degrees of documentation, be backed by a second home or investor property, or have a combination of attributes (such as large loan size and high LTV) that make the loan riskier. While subprime loans typically have FICO scores below 660, the loan programs and grades are highly lender-specific. One lender might consider a loan with a 620 FICO to be a B-rated loan, while another lender would grade the same loan higher or lower, especially if the other attributes of the loan (such as the LTV) are higher or lower than average levels.

Interest Rate Type

Fixed rate mortgages have an interest rate (or note rate) that is set at the closing of the loan (or, more accurately, when the rate is “locked”), and is constant for the loan’s term. Based on the loan’s balance, interest rate, and term, a payment schedule effective over the life of the loan is calculated to amortize the principal balance.

Adjustable rate mortgages (ARMs), as the name implies, have note rates that change over the life of the loan. The note rate is based on both the movement of an underlying rate (the index) and a spread over the index (the margin) required for the particular loan program. A number of different indexes can be used as a reference rate in determining the loan’s note rate the loan “resets,” including the London Interbank Offering Rate (LIBOR), one-year Constant Maturity Treasury (CMT), or the 12-month Moving Treasury Average (MTA), a rate calculated from monthly averages of the one-year CMT. The loan’s note rate resets at the end of the initial period and subsequently resets periodically, subject to caps and floors that limit how much the loan’s note rate can change. ARMs most frequently are structured to reset annually, although some products reset on a monthly or semiannual basis. Since the loan’s rate and payment can (and often does) reset higher, the borrower can experience “payment shock” if the monthly payment increases significantly.

Traditionally, ARMs had a one-year initial period where the start rate was effective, often referred to as the “teaser” rate (since the rate was set at a relatively low rate in order to entice borrowers.) The loans reset at the end of the teaser period, and continued to reset annually for the life of the loan. One-year ARMs, however, are no longer popular products, and have been replaced by loans that have features more appealing to borrowers.

At this writing, the ARM market is dominated by two different types of loans. One is the fixed-period ARM or hybrid ARM, which have fixed initial rates that are effective for longer periods of time (3-, 5-7-, and 10-years) after funding. At the end of the initial fixed rate period, the loans reset in a fashion very similar to that of more traditional ARM loans. Hybrid ARMs typically have three rate caps: initial cap, periodic cap, and life cap. The initial cap and periodic cap limit how much the note rate of the loans can change at the end of the fixed period and at each subsequent reset, respectively, while the life cap dictates the maximum level of the note rate.

At the opposite end of the spectrum is the payment-option ARM or negative amortization ARM. Such products begin with a very low teaser rate. While the rate adjusts monthly, the minimum payment is only adjusted on an annual basis and is subject to a payment cap that limits how much the loan’s payment can change at the reset. In instances where the payment made is not sufficient to cover the interest due on the loan, the loan’s balance increases in a phenomenon called “negative amortization.” (The mechanics of negative amortization loans are addressed in more depth later in this chapter.)

Amortization Type

Traditionally, both fixed and adjustable rate mortgages were fully amortizing loans, indicating that the obligor’s principal and interest payments are calculated in equal increments to pay off the loan over the stated term. Fully amortizing, fixed rate loans have a payment that is constant over the life of the loan. Since the payments on ARMs adjust periodically, their payments are recalculated at each reset for the loan’s remaining balance at the new effective rate in a process called recasting the loan.

A recent trend in the market, however, has been the growi...

Table of contents

• THE FRANK J. FABOZZI SERIES
• Title Page
• Copyright Page
• Dedication
• Preface
• About the Authors
• PART One - Introduction to Mortgage and MBS Markets
• PART Two - Prepayment and Default Metrics and Behavior
• PART Three - Structuring
• PART Four - Valuation and Analysis
• APPENDIX - An Option-Theoretic Approach to Valuing MBS
• Index