Professor Roubini should realize that you don't pay taxes on losses, and the funds available for loan losses are much higher than $362 billion. The IMF figure includes dividends, which you don't pay if you are in financial difficulty and loss provisions. In 1Q2008, BAC had about $18 billion in loan losses and pre tax, pre dividend earnings and Wells had about $10 billion. That's $28 billion for the two per quarter or or $224 billion over the two years from these two banks alone. This figure may be way too optimistic, but $150 billion from the two banks certainly isn't.
The IMF recently estimated that retained earnings (after taxes and dividends) for all US banks – not just these 19 ones – would be only $300 bn total over the 2009-2010 period. The stress tests – instead – assumed much higher retained earnings - $362 bn - for these 19 banks alone for the 2009-2010 period in the more adverse scenario. Since these 19 banks account for about half of US banks assets if one were to use the IMF estimate of net retained earnings for these 19 banks their net retained earnings for 2009-2010 would be $150 bn rather than the $362 bn assumed by the regulators. While the IMF may have been too conservative in its estimates of net retained earnings it appears that regulators may have been too generous to these 19 banks in forecasting their earnings in an adverse scenario.
Some of the banks may have to book huge portions of their pre tax, pre provision earnings but that is a big number. Just consider the $8 trillion in RWA and use a conservative net interest rate margin (say 2% per year) and you end up with $320 billion over the two years.