without regard for the longer-term consequences for systemic stability. Finally, he
concludes that there is an urgent need to limit leverage, by both borrowers and
the financial institutions that often are all too willing to lend to them.
How was it possible that securities backed by subprime debt—less than prime
quality loans—gained such popularity until the middle of 2007? In chapter 3
Mason answers that question, in part, by explaining how three financial “innova-
tions”—in the securities themselves and in the institutions that were formed to
sell or hold them—contributed to the acceptance of those securities and laid the
foundation for the crisis that followed. Ironically, each of the innovations also
proved to be a victim of the crisis.
The first such innovation is the collateralized debt obligation (CDO), a refine-
ment of the mortgage-backed security (MBS), a pioneering financial innovation
of the 1970s. In the typical (pass-through) MBS structure, investors receive, on a
pro rata basis, the principal and interest payments on the underlying mortgages.
In later innovations, MBSs were structured into various “tranches,” with the top
layer having first claim to the mortgage payments and with additional payments
cascading to each lower tranche after the claims of the more senior tranches had
been fully satisfied. The CDO differs from the MBS in several respects: the pools
of assets securitized by CDOs are actively managed rather than static; CDO
transactions often are closed before the pool of underlying assets is fully formed;
and CDOs often contain far fewer assets than conventional MBSs. As a result of
those features, the value of a CDO tranche is much more opaque than the value
of an MBS tranche. Moreover, secondary markets in CDOs are thinner than
those for MBSs; thus prices of CDO tranches can be much more volatile than
those of MBS tranches. Mason is critical (as are many others) of the credit rating
agencies, whose excessively optimistic ratings of CDO tranches facilitated their
easy sale to investors.
Although created in the late 1980s, structured investment vehicles (SIVs), the
second key innovation that Mason singles out, did not become popular until the
middle of this decade, when commercial banks discovered their advantages as an
off–balance sheet means of financing the purchase of CDOs and other structured
products that the banks manufactured and marketed. The typical SIV was funded
by asset-backed commercial paper (ABCP), which, until the subprime mortgage
market collapsed, was readily sold to investors seeking highly rated, short-term
securities promising higher returns than those available on more traditional
money market instruments. By funding long-term assets with short-term liabili-
ties, SIVs were vulnerable to funding risk. They could function only as long as
investors were willing to purchase (or roll over their purchases of) ABCP. More-
over, SIVs had relatively thin capital cushions, at 5 to 10 percent of assets, which
4 yasuyuki fuchita, richard j. herring, and robert e. litan
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