September 15, 2009
Unlike tranches of synthetic CDOs, that depend only on the defaults of the underlying securities, tranches of cashflow CDOs also depend on the interest cash flows from the coupons of the securities. Whilst fast, accurate, (semi-)analytic methods exist for pricing synthetic CDO tranches (Hull and White 2004), no equivalent methods exist for pricing cashflow CDO tranches because of their dependence on both principal and interest waterfalls. We introduce an analytical approximation that renders cashflow CDOs amenable to (semi-)analytic pricing. The complication of needing the joint distribution of interest and outstanding notional is reduced to needing only their marginal distributions. We show that our analytic approximation is globally valid with bounded errors that are small in most cases. Furthermore, our approach can be extended to more detailed structural features such as interest coverage tests and over-collateralization tests. We present results from realistic cashflow CDO examples.
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