One brutal sentence embodies the bleak state of money in America.

"The bottom half of Americans combined have a negative net worth," Ben Steverman wrote in a recent Bloomberg article.

This comment was based on the research of the French economist Gabriel Zucman, a "wealth detective" who studies wealth inequality and finds the secret money stashes of the richest people.

In the US, the rich are getting increasingly richer while the middle class and the poor get poorer.

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One brutal sentence sums up the dismal state of wealth disparity in the US.

"The bottom half of Americans combined have a negative net worth," Ben Steverman wrote in a recent Bloomberg article.

This statement is based on the research of the economists Emmanuel Saez and Gabriel Zucman, who study wealth inequality. Zucman is a "wealth detective" who spends hours combing through spreadsheets of tax tables, macroeconomic datasets, and international money-flow calculations to find the secret money stashes of the richest people.

Saez and Zucman's research on wealth inequality also found that 20% of American wealth is controlled by the top 0.1% of taxpayers — or about 170,000 families. The top 1% controls about 39% of the country's wealth, and the bottom 90% holds only 26%, despite years of economic growth in the US overall.

"The pie has not become bigger" in the US, Zucman told Bloomberg. "It's just that a bigger slice is going to the top."

Read more: Nearly half of Americans earning $100,000 or more think they're middle class — and it shows that class in America isn't just about money

These statistics are perhaps not surprising considering how many Americans are weighed down by substantial student debt. Millennials are saddled with more than $1 trillion of student-loan debt, Business Insider's Callum Burroughs previously reported.

And it's not just millennials who are suffering. More than 3 million Americans age 60 and older are still paying off their student loans, INSIDER's Kelly McLaughlin recently reported.

Credit-card debt is also on the rise. More than 40% of US households carry credit-card debt, and the average debt balance is $5,700, according to a 2018 report from ValuePenguin.

And about one-fifth of Americans don't have any money saved up, according to a Bankrate survey.

Economists have been sounding the alarm on the ballooning wealth inequality in the US

Thomas Piketty, a leading French economist and one of Zucman's former professors, has been spotlighting findings from the 2018 World Inequality Report, which he coauthored.

—World Inequality Lab | WID.world (@WIL_inequality) December 14, 2017

The authors found that while the income of the top 1% of American taxpayers made up 11% of the national income in 1980, it now makes up more than 20% of the country's income.

And the income of the bottom half of Americans, which was 20% of the national income in 1980, has fallen to just 12%.

In other words, the country's rich have been getting increasingly richer while the middle class and the poor get poorer.

Read more: A simple chart shows what some economists consider to be the 'most striking development' in 40 years of the US economy

While wealth inequality has also been rising in Europe, Business Insider's Richard Feloni wrote, "this particular rise of the top 1% paralleling the fall of the bottom 50% is unique to the US."

Politicians such as Bernie Sanders, who has consulted Zucman and Saez's data, and Elizabeth Warren have proposed substantially raising taxes on the wealthiest Americans in order to tackle the vast disparity of wealth in the US. Other solutions suggested by economists include investing in universal childcare and free college, dramatically expanding Social Security, and raising the federal minimum wage.