Fixed Income

Fundamental Differences Between Agency and Non-Agency Mortgage-Backed Securities

Topics - Fixed Income

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Fundamental Differences Between Agency and Non-Agency Mortgage-Backed Securities

Chapter in Whole Loan CMOs (Frank J. Fabozzi Associates, 1995)

The most important differences between agency and non-agency mortgage-backed securities (MBS) are the extra yield available on the non-agencies and the chance of default on the non-agencies. This trade-off is easy to understand. An investor assumes the risk of default in order to get the benefit of extra yield.

If these were the only differences between agencies and non-agencies, choosing between them would be straightforward. The investor would weigh the estimate of the probability of default against the benefit of the extra yield. Life is not that simple, however. There are many differences between agency and non-agency MBS that can affect our opinion about their relative value and risk.

These differences vary in their impact, but have several things in common. First, each one has a negative effect on non-agency MBS value. Second, they hurt the value of non-agency MBS because they add to the negative convexity already present in most mortgage-backed securities.

None of these differences implies that an investor should avoid non-agency MBS. The substantial spreads available in non-agency products may well compensate — even overcompensate — for the features we discuss. At the same time, it is important to understand the special characteristics of non-agency MBS.

This chapter explains and illustrates these differences between agency and non-agency MBS using a simple example. We explain the differences in detail, and we attempt to put in perspective the magnitude of each effect on the value of non-agency MBS.

This document is not intended to, and does not relate specifically to any investment strategy or product that AQR offers. It is being provided merely to provide a framework to assist in the implementation of an investor’s own analysis and an investor’s own view on the topic discussed herein.

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This material is not research and should not be treated as research. This paper does not represent valuation judgments with respect to any financial instrument, issuer, security or sector that may be described or referenced herein and does not represent a formal or official view of AQR. The views expressed reflect the current views as of the date hereof and neither the author nor AQR undertakes to advise you of any changes in the views expressed herein. 

The information contained herein is only as current as of the date indicated, and may be superseded by subsequent market events or for other reasons. Charts and graphs provided herein are for illustrative purposes only. The information in this presentation has been developed internally and/or obtained from sources believed to be reliable; however, neither AQR nor the author guarantees the accuracy, adequacy or completeness of such information. Nothing contained herein constitutes investment, legal, tax or other advice nor is it to be relied on in making an investment or other decision. There can be no assurance that an investment strategy will be successful. Historic market trends are not reliable indicators of actual future market behavior or future performance of any particular investment which may differ materially, and should not be relied upon as such. Diversification does not eliminate the risk of experiencing investment losses.

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