Greatest quarterly loss by a company (inflation adjusted)

The largest quarterly loss ever reported by a publicly traded company is $61.659 bn (£31.011 bn) posted for Q4 2008 by insurance company American International Group on 2 March 2009. This is the equivalent to a loss of $73.14 bn (£56.18 bn) in 2018 when adjusted for inflation

AIG's massive loss came from its heavy investment in the market surrounding financial products called Collateralized Debt Obligations (CDOs). These are packages of financial assets (loans, bonds or mortgages) that serve as collateral for the value of the product, which is then traded on the open market. The assets that were pooled in CDOs were often high-risk ("sub-prime") debt, such as large mortgages granted to people with an at-best marginal ability to pay them back. In 2008 the US housing market went into decline, making many of these "sub-prime" mortgages worthless and sending the value of CDOs into freefall. This event triggered a global economic downturn known as the "sub-prime crisis" or the "credit crunch".

AIG was caught up in this crash because it was in the business of selling complex derivatives called Credit Default Swaps (CDS). These effectively served as insurance against a company's investments going bad. When the CDO market collapsed, AIG was obligated to pay out billions of dollars to customers that had bought CDS agreements for their CDO investments.