ABSTRACT: In this paper, we provide an overview of the subprime mortgage securitization process and the seven key informational frictions that arise. We discuss the ways that market participants work to minimize these frictions and speculate on how this process broke down. We continue with a complete picture of the subprime borrower and the subprime loan, discussing both predatory borrowing and predatory lending.

We present the key structural features of a typical subprime securitization, document how rating agencies assign credit ratings to mortgage-backed securities, and outline how these agencies monitor the performance of mortgage pools over time. Throughout the paper, we draw upon the example of a mortgage pool securitized by New Century Financial during 2006.

Key words: subprime mortgage credit, securitization, rating agencies, principal agent, moral hazard

Introduction:

How does one securitize a pool of mortgages, especially subprime mortgages? What is the process from origination of the loan or mortgage to the selling of debt instruments backed by a pool of those mortgages? What problems creep up in this process, and what are the mechanisms in place to mitigate those problems? This paper seeks to answer all of these questions. Along the way we provide an overview of the market and some of the key players, and provide an extensive discussion of the important role played by the credit rating agencies.

In Section 2, we provide a broad description of the securitization process and pay special attention to seven key frictions that need to be resolved. Several of these frictions involve moral hazard, adverse selection and principal-agent problems. We show how each of these frictions is worked out, though as evidenced by the recent problems in the subprime mortgage market, some of those solutions are imperfect. In Section 3, we provide an overview of subprime mortgage credit; our focus here is on the subprime borrower and the subprime loan.

We offer, as an example a pool of subprime mortgages New Century securitized in June 2006. We discuss how predatory lending and predatory borrowing (i.e. mortgage fraud) fit into the picture. Moreover, we examine subprime loan performance within this pool and the industry, speculate on the impact of payment reset, and explore the ABX and the role it plays. In Section 4, we examine subprime mortgage-backed securities, discuss the key structural features of a typical securitization, and, once again illustrate how this works with reference to the New Century securitization.

We finish with an examination of the credit rating and rating monitoring process in Section 5. Along the way we reflect on differences between corporate and structured credit ratings, the potential for pro-cyclical credit enhancement to amplify the housing cycle, and document the performance of subprime ratings. Finally, in Section 6, we review the extent to which investors rely upon on credit rating agencies views, and take as a typical example of an investor: the Ohio Police & Fire Pension Fund.

We reiterate that the views presented here are our own and not those of the Federal Reserve Bank of New York or the Federal Reserve System. And, while the paper focuses on subprime mortgage credit, note that there is little qualitative difference between the securitization and ratings process for Alt-A and home equity loans. Clearly, recent problems in mortgage markets are not confined to the subprime sector.

Download Understanding the Securitization of Subprime Mortgage Credit

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Federal Reserve Bank of New York Staff Reports
Understanding the Securitization of Subprime Mortgage Credit

Adam B. Ashcraft
Til Schuermann
Staff Report no. 318. March 2008

Conclusions:

While this paper focuses on the securitization of subprime mortgages, many of the basic issues – intermediation and the frictions it introduces – are generic to the securitization process, regardless of the underlying pool of assets. The credit rating agencies play an important role in resolving or at least mitigating several of these frictions.

Our view is that the rating of securities secured by subprime mortgage loans by credit rating agencies has been flawed. There is no question that there will be some painful consequences, but we think that the rating process can be fixed along the lines suggested in the text above.

However, it is important to understand that repairing the securitization process does not end with the rating agencies. The incentives of investors and investment managers need to be aligned. The structured investments of investment managers should be evaluated relative to an index of structured products in order to give the manager appropriate incentives to conduct his own due diligence. Either the originator or the arranger needs to retain unhedged equity tranche exposure to every securitization deal. And finally, originators should have adequate capital so that warranties and representations can be taken seriously.

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