Credit Suisse analysts estimate $321 billion in cumulative losses at Fannie Mae and Freddie Mac, based on a further 10% decline in home prices over the next year. Under that scenario, prices would flatten over the following year and experience a 3% annual appreciation going forward. But in its “stress scenario” Credit Suisse said the government-sponsored enterprises could lose as much as $448 billion, 11% higher than the Federal Housing Finance Agency estimate. Under the “stress scenario,” home prices would fall another 20% over the next two years. Analysts said the GSEs could draw another $122 billion to $249 billion from Treasury through 2013. That’s on top of the $148 billion already drawn and does not include dividend payments, which would add another $70 billion to $90 billion. Future delinquencies on the Fannie and Freddie books could reach between $408 billion in the base scenario analysts laid out and $464 billion in the stressed scenario. Also, analysts estimate that 76% of currently delinquent loans would eventually default with a 45% loss severity rate. Of these defaulting loans, 60% would qualify for a modification, and nearly half of the rest would redefault after the workout. As for mortgage putbacks, a growing concern among bank investors, Credit Suisse analysts suggest Fannie Mae and Freddie Mac could put back 5% of their cumulative delinquent loans to lenders. This translates to about $40 billion in bad mortgages the banks would have to buyback from Fannie and Freddie and reduces the losses to the GSEs by $15 billion to $20 billion. Write to Jon Prior.