The Black Swan: The Impact of the Highly Improbable · chapter 7 · id the-black-swan-c7-05-the-gaussian-copula-model-deve

“The Gaussian copula model developed by David X. Li (2000) was widely adopted by banks and rating agencies to price CDOs (collateralized debt obligations). Felix Salmon's 2009 Wired article called it 'The Formula That Killed Wall Street,' and the model's failure contributed to trillions of dollars in losses during the 2008 financial crisis.”

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Wikipedia: David X. Lisource alive

David X. Li pioneered the use of Gaussian copula models for pricing CDOs. His paper 'On Default Correlation: A Copula Function Approach' was published in 2000 and rapidly became the industry standard for CDO pricing.

Watts, 'The Gaussian Copula and the Financial Crisis'source alive

The Gaussian copula model dramatically underestimated the probability of correlated defaults. When housing markets declined simultaneously across the US, the correlation assumptions in CDO models failed catastrophically.

MacKenzie & Spears (2014), 'The Formula That Killed Wall Street', Social Studies of Sciencesource alive

Felix Salmon's Wired article described the Gaussian copula as 'a beautiful, but fatally flawed, model.' The formula's adoption was driven by its simplicity and tractability, not by evidence of its accuracy under stress conditions.

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