Commercial Mortgage Backed Securities: How Much Subordination is Enough?

Abstract

The commercial mortgage-backed security market has experienced rapid growth in recent years, but relatively little academic research has questioned the apparent success of the CMBS capital structure. In this paper, we study whether the recent growth in the CMBS market actually reflects the mitigation of a market imperfection, as some have suggested, or reflects ever thinner subordination levels, perhaps backed up by overly aggressive assumptions about future commercial real estate performance. Preliminary results from our analysis based on a multi-factor structural model of expected commercial mortage defaults indicate that, somewhat surprisingly, the optimal levels of subordination are lower than those observed in recent CMBS deals. One interpretation of these results is that, in the absence of a performance track record for securitized commercial mortgages, the subordination levels of early deals were set too high. Under this interpretation, our results imply that in the future the CMBS market will likely see further reductions in subordination and continued rapid growth. An indirect implication of this conclusion is that the CMBS capital structure does create value.