The equity that owners have in their homes is an important share of the net worth of American families. For most of the last 25 years, homeowners� equity has constituted about a quarter of total household wealth,about as much as their ownership of stocks (including the amounts in retirement accounts and mutual funds), and more than the value of unincorporated businesses and commercial and rental real estate combined.

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The P4 laboratory, on the campus of the Wuhan Institute of Virology, in Wuhan, in China's central Hubei province. (Hector Retamal/AFP via Getty Images)