The United States housing bubble is the economic bubble in many parts of the U.S. housing market that began roughly in 2001, especially in populous areas such as California, Florida, New York, Michigan , the suburbs of Chicago in the Midwest, the BosWash megalopolis, and the Southwest markets. It reached its peak in 2005 and then plateaued, and started deflating in 2006 and accelerated since. Greatly-increased foreclosure rates in 2006–2007 by U.S. homeowners unable to pay their mortgages caused a crisis in August 2007 for the subprime, Alt-A, CDO, CDX, mortgage, credit, hedge fund, and foreign bank markets.[2] The U.S. Treasury Secretary called the bursting housing bubble "the most significant risk to our economy."