This paper looks at different ways to fix the U.S. housing finance system after Fannie Mae and Freddie Mac failed. They consider changing how the government helps with mortgages, using private markets more, or creating new government mortgage guarantees. The researchers review the history of Fannie Mae and Freddie Mac, how they helped the housing market, and why they failed during the mortgage crisis. They also look at ideas from a 2011 U.S. Treasury report, plans for new government mortgage guarantees, and how private mortgage markets work in Europe.