Non-prime mortgages owned or guaranteed by Fannie Mae and Freddie Mac continued to gradually melt away in early 2011, although performance improved somewhat on Alt A mortgages. Combined, Fannie and Freddie had $447.33 billion in non-prime holdings at the end of the first quarter, down 17.3 percent from the same period in 2010, according to a new analysis by Inside Nonconforming Markets. Alt A mortgages accounted for 69.9 percent of the government-sponsored enterprises' exposure to non-prime loans. New business at the GSEs continued to meet high standards. The weighted-average loan-to-value ratio on mortgages guaranteed by... [Includes one data chart]