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A new study finds wealth inequality among U.S. households has nearly doubled over the past decade.

The analysis, performed by researchers at the University of Michigan, shows households in the 95th percentile of net worth had 13 times the wealth of the median household in 2003. By 2013, this disparity had increased almost twofold, with the wealthiest 5% of Americans holding 24 times that of the median.

In dollars terms, the median wealth of a US household was $87,992 in 2003, and by 2013 had decreased 36% to $56,335. In contrast, the richest 10% actually saw their net worth increase from 2003 to 2013, with the highest gains going to the top 5%. The median wealth of the households in the top five percent grew over 12% during the same time period, from $1,192,639 to $1,364,834.

The study also shows similar wealth inequality growth between median and poor households. In 2013, the 50th percentile held 17.6 times the wealth of the least wealthy 25%—over twice the disparity found in 2003.

A principal reason for the rapid increase in wealth disparity over the last 10 years is the different ways various economic groups invest their money. According to the study's lead author, Fabian T. Pfeffer, more than half of the median household's wealth in 2007 was in home equity. By comparison, the median household in the richest 5th percentile held only 16% of their wealth in home equity, with the lion's share being kept in real assets, including business assets (49%) and financial instruments like stocks and bonds (25%).

Pfeffer explains that because stocks have recovered more quickly than the real estate market—the S&P reached its pre-recession high in March of 2013, while home prices are still far from their 2006 peak—average households were hurt far more than richer Americans when the housing bubble popped. When home equity is excluded from household wealth, the impact of the housing crash on average Americans is especially clear. A median household's total net worth declined by $42,000 between 2007 and 2013, but their wealth held in non-real estate assets declined by only $6,900. The Great Recession's disproportionate impact on real estate allowed the richest households, who could afford to diversify their investments, to grow wealth even during a deflating housing market.

Source: YCharts

Another concern for middle class households is that many sold off investments during the recession in order meet expenses, and are now less able to enjoy the benefits of a recovering economy. "Part of the lack of recovery is that they [median American households] had to divest," says Pfeffer. "The troubles will stay with them for the next couple of decades as they try to reclaim these assets."

Will wealth inequality continue to increase at its current pace? Pfeffer believes it would take another deep recession for inequality to double again in the next 10 years, but says his research confirms what economists like best-selling author Thomas Piketty have been saying for years: that returns to capital have been increasing at a rapid pace over the last century, creating a persistently swelling gap between the wealth of the haves and the have-nots. "I don't see many hopefully signs that we're going to get back to where we were 10 years ago," Pfeffer says.

Some have claimed inequality is less important as long as all Americans see wealth gains over time. The rich may get richer faster, but that might not matter if the poor and middle class are also seeing their wealth increase. Pfeffer disagrees. A rising tide may lift all boats, but the Michigan professor points out that wealth not only tends to determine political influence, but also that wealth inequality greatly affects the opportunities available to the children of the middle class, especially in terms of education. "The further families pull apart [in net worth], the more disparate the opportunities become for their offspring," he says.