21st century, many industrialized countries, with a notable exception of Germany, experienced a major spike of household debt versus GDP around 2007–8, with the United States leading up to 2007; by 2017, the American ratio was second only to that of the United Kingdom. U.S. households made significant progress in deleveraging (reducing debt) post-crisis, much of it due to foreclosures and financial institution debt write-downs. By some measures, consumers began to add certain types of debt again in 2012, a sign that the economy may be improving as this borrowing supports consumption. Global economic impact The International Monetary Fund (IMF) reported in April 2012: "Household debt soared in the years leading up to the Great Recession. In advanced economies, during the five years preceding 2007, the ratio of household debt to income rose by an average of 39 percentage points, to 138 percent. In Denmark, Iceland, Ireland, the Netherlands, and Norway, debt peaked at more than 200 percent of household income. A surge in household debt to historic highs also occurred in emerging economies such as Estonia, Hungary, Latvia, and Lithuania. This occurred largely because the central banks implemented a prolonged period of artificially low policy interest rates, temporarily increasing the amount of debt that could be serviced with a given income. The leveraging up fueled a consumption boom that, ironically, boosted GDP in the countries in question, but represented not a sustainable 'boost to aggregate demand' but instead a mere pulling forward of consumption, as people took on new 30-40 year debt to pay for current year expenditures. The predictable fallout of this policy is the slow growth that these countries are experiencing today. At the time, the concurrent boom in both house prices and the stock market - as the prices of financed and financial assets were bid up by virtue of the same low rates - meant that household debt relative to assets held broadly stable, which masked households' growing exposure to the eventual sharp fall in asset prices. House prices in particular were vulnerable to sharp movements in policy rates in countries in which most mortgages are adjustable-rate, as 30-40 year loans are highly rate sensitive, house purchases are financed at 80-95% of the price, and only 4-5% of homes change owners in a year. Despite this low volume, the appraisal rules in most countries limit the number of times that a sale can serve as