There is a growing body of data that suggests banks have recognized only a fraction of the overall potential losses – approximately $50 billion to $75 billion so far on subprime debt alone. And a variety of estimates suggest that total subprime losses may be more than $300 billion before we’re through.

Fannie Mae is supposed to be prime, but it turns out that much of its loan book is made up of less than perfect credit.

Forbes reports that yesterday “Fannie Mae executives told analysts that 43.0%, or $946 million, of the $2.2 billion in losses incurred during the first quarter involved Alt-A loans. They also said that the company’s ‘Alt-A book will continue to drive an outsize portion of our overall credit losses.’