The report by the Institute for Policy Studies (IPS) warned that proposed tax reforms by Donald Trump would “exacerbate existing wealth disparities”, benefitting the top 1%.
It also suggested reducing the concentration of private wealth by taxing the wealthiest households, the money from which could be invested in expanding wealth-building opportunities in the economy.
“If left unchecked, wealth will continue to accumulate into fewer and fewer hands, a trend we’ve been witnessing for decades,” said IPS’ director of the project on opportunity and taxation Josh Hoxie, who co-authored the report.
“The time to reverse this trend is past due.”
Senior scholar at the IPS Chuck Collins said there was a “billionaire problem in the United States” and called the concentration of wealth a “troubling trend” for democratic society.
Using data from this year’s Forbes 400 and the Federal Reserve’s 2016 Survey of Consumer Finances, the IPS found that the top 25 billionaires in the US held $1trn (£763bn) in wealth, equal to that of 56% of the population.
Billionaires making up the entire Forbes 400 list owned $2.68trn (£2trn) in wealth, which is more wealth than 64% of the US population.
Additionally, the report showed that almost one in five (19%) US households are classed as being “underwater” due to having zero or negative net worth.
Inequality was found to be worse among minorities, with three in 10 black and 27% of Latino families having zero or negative wealth, whereas only 14% of white households had a net worth of zero or below.
Only two members of the Forbes 400 list were African-Americans: media mogul Oprah Winfrey (ranked 264, with $3bn in wealth) and businessman and investor Robert Smith (ranked 226, with $3.3bn).
Meanwhile, five members of the list were of a Latino background, including real estate developer Jorge Pérez (ranked 264, with $3bn) and Los Angeles Angels baseball team owner Arturo Moreno (ranked 324, with $2.5bn).