The 2000s United States housing bubble was a real-estate bubble affecting over half of the U.S. states. It was the impetus for the subprime mortgage crisis. Housing prices peaked in early 2006, started to decline in 2006 and 2007, and reached new lows in 2011. On December 30, 2008, the Case–Shiller home price index reported its largest price drop in its history. The credit crisis resulting from the bursting of the housing bubble is an important cause of the Great Recession in the United States. Increased foreclosure rates in 2006–2007 among U.S. homeowners led to a crisis in August 2008 for the subprime, Alt-A, collateralized debt obligation (CDO), mortgage, credit, hedge fund, and foreign bank markets. In October 2007, Henry Paulson, the U.S. Secretary of the Treasury, called the bursting housing bubble "the most significant risk to our economy". Any collapse of the U.S. housing bubble has a direct impact not only on home valuations, but mortgage markets, home builders, real estate, home supply retail outlets, Wall Street hedge funds held by large institutional investors, and foreign banks, increasing the risk of a nationwide recession. Concerns about the impact of the collapsing housing and credit markets on the larger U.S. economy caused President George W. Bush and the Chairman of the Federal Reserve Ben Bernanke to announce a limited bailout of the U.S. housing market for homeowners who were unable to pay their mortgage debts. In 2008 alone, the United States government allocated over $900 billion to special loans and rescues related to the U.S. housing bubble. This was shared between the public sector and the private sector. Because of the large market share of Federal National Mortgage Association (Fannie Mae) and the Federal Home Loan Mortgage Corporation (Freddie Mac) (both of which are government-sponsored enterprises) as well as the Federal Housing Administration, they received a substantial share of government support, even though their mortgages were more conservatively underwritten and actually performed better than those of the private sector. Background Land prices contributed much more to the price increases than did structures. This can be seen in the building cost index in Fig. 1. An estimate of land value for a house can be derived by subtracting the replacement value of the structure, adjusted for depreciation, from the home price. Using this methodology, Davis and Palumbo calculated land values for 46 U.S. metro areas, which can be found at the