97% of All U.S. Mortgages are Backed by the Government

I heard a recent talk by Richard Wolff – Professor of Economics Emeritus at the University of Massachusetts in Amherst (PhD in Economics from Yale) – where Wolff said that 97% of all U.S. mortgages are either written or guaranteed by the government.
http://www.ritholtz.com/blog/2011/03/97-of-all-u-s-mortgages-are-backed-by-the-government/