FASB 157 was passed to help investors and regulators understand how accurate a given company's asset estimates truly were. Many firms (including some of the largest in terms of assets) had to write down billions of dollars in hard-to-value Level 3 assets following the subprime meltdown and related credit crisis, which began in late 2006. By making companies report to investors the breakdown of assets, they allow investors to potentially see what percentage of the balance sheet could be open to revaluation or susceptible to sudden write-downs.