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Early in the debate, Sen. Bernie Sanders used an inaccurate figure that had been provided to his campaign by a progressive think tank that, among other things, keeps track of the fortunes of billionaires.

“In the last three years, last three years, billionaires in this country saw an $850 billion increase in their wealth,” Sanders said.

Facts First: The think tank that provided the figure says it is wrong, and says it takes responsibility for the error.

Sanders was relying on a figure from the Institute for Policy Studies, according to the think tank senior scholar Chuck Collins but the number was inflated. “We informed Senator Sanders that US billionaires increased their wealth since Trump’s election by $850 billion. Our updated number is $710 billion, an increase of 30 percent,” Collins told CNN during the debate.

“Senator Sanders was accurately using information that we provided, so we at Institute for Policy Studies are responsible for the error,” Collins added.

He said that in 2016, there were 541 US billionaires with wealth totaling about $2.4 trillion. In 2019, he said, there were 607 US billionaires with wealth totaling about $3.1 trillion.

Collins said he informed the Sanders campaign on Tuesday morning that there had been an error, after CNN contacted the campaign to ask for the source for the $850 billion number. It is not clear, though, whether Sanders himself was informed of the error prior to the debate.

There is no doubt that the wealthiest Americans have gotten wealthier under President Trump, though others have also gained.

According to the Federal Reserve, the combined wealth of the top 1% of American households increased 18% from the fourth quarter of 2016 to the third quarter of 2019 — from $29.18 to $34.53 trillion. The combined wealth of the bottom 50% of households increased 55%, but from a much smaller starting point — from $1.08 trillion to $1.67 trillion — and spread out across many more households.