IMF: Re-Remics are being used to resecuritize senior private-label mortgage-backed security (MBS) tranches that have been downgraded from their initial AAA levels. In a typical Re-Remic, a downgraded tranche is subdivided into a new AAA-rated senior tranche and a lower-rated mezzanine tranche (see figure). About $25 billion were issued during the first half of 2009, mostly against MBSs backed by prime mortgages. Given that most of the AAA privatelabel MBS tranches issued between 2005 and 2007 have been downgraded, the potential for this market to grow is substantial. However, although these transactions are playing a useful role in dealing with the overhang of legacy assets, they are partly driven by rating/regulatory arbitrage.

Re-Remic issuance is being driven by a number of factors, including the need to maintain the AAA ratings that many investors require to hold these securities. Maintaining AAA status canresult in substantial capital requirement reductions.For example, the new Basel II risk weight on a BB-rated tranche is 350 percent under the standardized approach, whereas it is 40 percent on an AAA-rated resecuritization. Also, for banks and insurers, big rating downgrades can trigger “other-than-temporary-impairments,” which have to be recognized immediately through the income statement. These consequences can be avoided by replacing the downgraded securities with new AAA-rated Re-Remics. In the figure, the new AAA-rated senior tranche comprises 70 percent of the structure, with a mezzanine tranche that absorbs the first 30 percent of losses. Additional credit enhancement is provided by an option for the new senior tranche to be resubdivided into two “exchange classes” should it lose its AAA rating. Also, there is a hedge fund demand for the mezzanine tranches as a means to take a leveraged credit bet. The holder of the senior tranche that was downgraded to BB could then hold the new AAA tranche, and sell the mezzanine tranche to an investor desiring distressed securities. Hence, only 30 percent of the original holding is sold at distress prices, and the risk-weighted par value of the holding goes from 350 to 28 percent (70 percent of 40 percent). Even if the bank were to retain the mezzanine tranche, the riskweighted par value could still be less than the original 350 percent.
For example, for single security-backed Re-Remics, the default probability-based rating methodologies used by DBRS, Fitch, and S&P will typically pass the underlying bond’s rating through to the new mezzanine tranche (emphasis mine). Hence, in the example transaction, the total riskweighted par value would decline from 350 to 223 percent (70 percent of 40 percent on the AAA-rated tranche plus 30 percent of 650 percent on the BB-rated tranche).¹ In this regard, it is notable that Moody’s has been virtually shut out of the Re-Remic rating business, possibly because it rates on the basis of expected loss, which is tougher on mezzanine tranches than the default probability basis (Fender and Kiff, 2005), and thus issuers prefer not to have Moody’s rate their potential securitization.

Although Re-Remics and similar repackaging transactions are playing useful roles in dealing with the legacy asset overhang, they also serve to illustrate the vulnerability of ratings-based regulations to gaming and shopping. Also, these new securities remain exposed to further downgrades if economic and housing market conditions worsen. However, the information underpinning these securitizations and the methodologies applied to their ratings are likely more robust than before and thus pricing is likely to reflect risks more appropriately.

Source: Restarting Securitization Markets: Policy Proposals and Pitfalls, IMF

¹ The new risk weights would be even lower if they were calculated with the securitization exposure weights (20 and 350 percent, respectively, on the AAA and BB tranches), rather than the resecuritization exposure weights (40 and 650 percent). The Basel Committee has defined a resecuritization as a securitization where “at least one of the underlying exposures is a securitization exposure” (BCBS, 2009), but some market participants are hopeful that single-security repacks may not be considered resecuritizations (Mayer Brown, 2009).