Both Fannie Mae and Freddie Mac continued to shrink their mortgage portfolios as required by government regulators during the first quarter of 2011 even as the two government-sponsored enterprises posted dramatically different earnings reports for the first three months of the year. Under the terms of the purchase agreement with the Treasury Department and under Federal Housing Finance Agency regulation, both Fannie and Freddie’s mortgage-related investments portfolio are subject to a cap that decreases by 10 percent each year until each portfolio reaches $250 billion. By Dec. 31, 2011, neither company will be able to hold an unpaid principal balance for mortgage-related investments that exceeds $729 billion. “FHFA has stated that we will not be a substantial buyer or seller of mortgages for... [Includes one data chart]