In all these areas, what looked like an established trend that economic agents relied on has changed very quickly, triggering a chain of reactions that few people had anticipated and leading policy makers to take prompt and decisive action: •  First, the mortgage market meltdown in the United States disproved the previous thesis that house prices would not fall nation-wide.
Such belief was widely shared among investors and misled them to lend abundantly to households that did not have sufficient resources. There are of course different ways to compute the change in house prices; according to some measures 1 , house prices in the United States nearly doubled in nominal terms between the early 2000 and 2006.