The federal subsidy Fannie Mae and Freddie Mac derive from the ties to the federal government has nearly doubled in the past three years and now totals $19.9 billion a year, the Congressional Budget Office disclosed last week. In a speech delivered before Women in Housing Finance, CBO Director Douglas Holtz-Eakin said the dramatic increase in the GSEs’ subsidy was due to a sharp rise in the volume of loans and mortgage-backed securities held