The Great Recession was the period marked by a sharp decline in economic activity during the late 2000s. The Great Recession began in 2007 when the U.S. housing market went from boom to bust, and large amounts of mortgage-backed securities (MBSs) and derivatives lost significant value.

What Is a CDO?

A collateralized debt obligation (CDO) is a type of financial instrument that pays investors from a pool of revenue-generating sources. One way to imagine a CDO is a box into which monthly payments are made from multiple mortgages. It is usually divided into three tranches, each representing different risk levels.

Key Takeaways

  • CDOs were a leading cause of the Great Recession but not the only cause.
  • A CDO is a financial instrument that pays investors from a pool of revenue-generating sources.
  • A decline in the value of CDO's underlying commodities, mainly mortgages, caused financial devastation during the financial crisis. 
  • CDOs pay higher than T-Bills and are an attractive investment for institutional investors.
  • CDOs proliferated through the shadow banking community in the years leading up to the Great Recession.
  • During the Great Recession, the collateralized debt markets collapsed as millions of homeowners defaulted on their mortgage loans.

Understanding the Role of CDOs in the Great Recession

Although CDOs played a leading role in the Great Recession, they were not the only cause of the disruption, nor were they the only exotic financial instrument being used at the time.

CDOs are risky by design, and the decline in value of their underlying commodities, mainly mortgages, resulted in significant losses for many during the financial crisis. As borrowers make payments on their mortgages, the box fills with cash. Once a threshold has been reached, such as 60% of the month's commitment, bottom-tranch investors are permitted to withdraw their shares.

Commitment levels such as 80% or 90% may be the thresholds for higher-tranch investors to withdraw their shares. Bottom-tranch investing in CDOs is attractive to institutional investors because the instrument pays at a rate that is higher than T-Bills despite being considered almost risk-free.

The 2007 Bankruptcy Bill reformed personal bankruptcy and increased the cost, leaving insolvent homeowners with no recourse when they found themselves unable to pay their mortgages.

What Went Wrong?

For the years prior to the 2007-2008 crisis, CDOs proliferated throughout what is sometimes called the shadow banking community. Shadow banks facilitate the creation of credit across the global financial system, but members are not subject to regulatory oversight.

The shadow banking system also refers to unregulated activities by regulated institutions. Hedge funds, unlisted derivatives, and other unlisted instruments are intermediaries not subject to regulation. Credit default swaps are examples of unregulated activities by regulated institutions.

As the practice of merging assets and splitting the risks they represented grew and flourished, the economics of CDOs became ever more elaborate and rarefied. A CDO-squared, for example, were composed of the middle tranches of multiple regular CDOs, which have been aggregated to create more "risk-free" investments for banks, hedge funds, and other large investors looking for ballast.

The middle tranches of these investments could then be combined into a still more abstracted instrument called a CDO-cubed. By this point, the returns investors were drawing were three times removed from the underlying commodity, which was often home mortgages.

Mortgages as Underlying Commodities

The strength of a CDO is also its weakness. By combining the risk from debt instruments, CDOs make it possible to recycle risky debt into AAA-rated bonds that are considered safe for retirement investing and for meeting reserve capital requirements. This helped to encourage the issuance of subprime, and sometimes subpar, mortgages to borrowers who were unlikely to make good on their payments.

Fast Fact

CDOs make it possible to recycle risky debt into AAA-rated bonds that are considered safe for retirement investing and for meeting reserve capital requirements.

All of this culminated in the passage of the 2007 Bankruptcy Bill. This bill reformed the practice of personal bankruptcy with an eye toward limiting abuse of the system. The bill also increased the cost of personal bankruptcy and left insolvent homeowners without recourse when they found themselves unable to pay their mortgages.

What followed was a domino-like collapse of the intricate network of promises that made up the collateralized debt markets. As millions of homeowners defaulted, CDOs failed to reach their middle and upper tranches, CDO-squared and CDO-cubed investors lost money on so-called "riskless" investments.