A report from the Census Bureau is the latest evidence that the rich are getting richer while the poor get poorer.
The study divided the U.S. into five groups, from wealthiest to poorest.
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The median net worth of the richest households rose 11 percent between 2000 and 2011, to $630,754. The next-wealthiest group's net worth also rose.
But because wealth dropped for the majority of Americans, the median household net worth for the country overall declined about 7 percent to $68,828.
A rebound in the stock market and rising home values after the housing bust helped richer Americans regain their wealth since the recession, which began in December 2007 and ended in June 2009.
But the bottom 20 percent owed more than they had and were worse off in 2011 than they were in 2000. In 2011, the median net worth of the poorest Americans was negative $6,029, compared with negative $905 a decade before.
There was also disparity between races and ages. The median net worth for whites, overall, rose between 2000 and 2011, but fell for black and Hispanic Americans, the Census Bureau said Thursday.
For those under 55 years old, median net worth fell. Median net worth rose for people 65 and older, while there was almost no change for those between 55 and 64.
The report was compiled using surveys done by the Census. It included net worth based on stocks, money in the bank, home values, retirement accounts and other assets in its measurement of net worth. It also took into account debts, such as home mortgages, car loans, credit card debt and student loans.
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