Juan Ospina and Harald Uhlig have posted Mortgage-Backed Securities and the Financial Crisis of 2008: A Post-Mortem to SSRN. Given that the market for private-label MBS pretty much died by 2008, the title is apt. The paper presents a challenge to many of the standard narratives that have developed to explain the causes of the subprime crisis and the broader financial crisis that followed. Other researchers in this area will surely take up the gauntlet thrown down by this paper. Hopefully, we will collectively come up with the right narrative to explain the whole mess. The paper opens,
Gradually, the deep financial crisis of 2008 is in the rearview mirror. With that, standard narratives have emerged, which will inform and influence policy choices and public perception in the future for a long time to come. For that reason, it is all the more important to examine these narratives with the distance of time and available data, as many of these narratives were created in the heat of the moment.
One such standard narrative has it that the financial meltdown of 2008 was caused by an overextension of mortgages to weak borrowers, repackaged and then sold to willing lenders drawn in by faulty risk ratings for these mortgage back securities. To many, mortgage backed securities and rating agencies became the key villains of that financial crisis. In particular, rating agencies were blamed for assigning the coveted AAA rating to many securities, which did not deserve it, particularly in the subprime segment of the market, and that these ratings then lead to substantial losses for institutional investors, who needed to invest in safe assets and who mistakenly put their trust in these misguided ratings.
In this paper, we re-examine this narrative. We seek to address two questions in particular. First, were these mortgage backed securities bad investments? Second, were the ratings wrong? We answer these questions, using a new and detailed data set on the universe of non-agency residential mortgage backed securities (RMBS), obtained by devoting considerable work to carefully assembling data from Bloomberg and other sources. This data set allows us to examine the actual repayment stream and losses on principal on these securities up to 2014, and thus with a considerable distance since the crisis events. In essence, we provide a post-mortem on a market that many believe to have died in 2008. We find that the conventional narrative needs substantial rewriting: the ratings and the losses were not nearly as bad as this narrative would lead one to believe.
Specifically, we calculate the ex-post realized losses as well as ex-post realized return on investing on par in these mortgage backed securities, under various assumptions of the losses for the remaining life time of the securities. We compare these realized returns to their ratings in 2008 and their promised loss distributions, according to tables available from the rating agencies. We shall investigate, whether ratings were a sufficient statistic (to the degree that a discretized rating can be) or whether they were, essentially, just “noise”, given information already available to market participants at the time of investing such as ratings of borrowers.
We establish seven facts. First, the bulk of these securities was rated AAA. Second, AAA securities did ok: on average, their total cumulated losses up to 2013 are 2.3 percent. Third, the subprime AAA-rated segment did particularly well. Fourth, later vintages did worse than earlier vintages, except for subprime AAA securities. Fifth, the bulk of the losses were concentrated on a small share of all securities. Sixth, the misrating for AAA securities was modest. Seventh, controlling for a home price bust, a home price boom was good for the repayment on these securities. (1-2)