To do this, the Fed created hypothetical scenarios that simulate adverse economic conditions, such as high unemployment, falling home prices, and a sharp decline in GDP. The scenarios also incorporate factors such as changes in interest rates, exchange rates, and commodity prices.
Back in 2008, banks were ignoring the houses foreclosing in their own neighborhoods while taking free money in the form of highly-leveraged derivatives based on false mortgage grades from suspect rating companies. This time it's different.
Depositor flight to higher-yielding alternatives will continue. And since the bonds bank’s own will be permanently worth less than the deposits they received to buy them, the only way to prevent the inevitable panic is to guarantee all deposits.