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CDO issuance grew from an estimated $20 billion in Q1 2004 to its peak of over $180 billion by Q1 2007, then declined back under $20 billion by Q1 2008. Further, the credit quality of CDO's declined from 2000 to 2007, as the level of subprime and other non-prime mortgage debt increased from 5% to 36% of CDO assets. As described in the section on subprime lending, the CDS and portfolio of CDS called synthetic CDO enabled a theoretically infinite amount to be wagered on the finite value of housing loans outstanding, provided that buyers and sellers of the derivatives could be found. For example, buying a CDS to insure a CDO ended up giving the seller the same risk as if they owned the CDO, when those CDO's became worthless.

What was the estimated value of CDO issuance in Q1 2004?
$20 billion