The income gap between the richest 1% of Americans and the other 99% widened to a record margin in 2012, according to an analysis of tax filings.
The top 1% of US earners collected 19.3% of household income, breaking a record previously set in 1927.
Income inequality in the US has been growing for almost three decades.
Overall, the pre-tax incomes of the top 1% of households rose 19.6% compared to a 1% increase for the rest of Americans.
And the top 10% of richest households represented just under half of all income in the year, according to the analysis.
Emmanuel Saez at the University of California, Berkeley, one of the economists who analysed the tax data, said the rise may have been in part because of sales of stock to avoid higher capital gains taxes in January.
Mr Saez wrote in an analysis that despite recent policy changes aiming at lessening income inequality, the measures were relatively small in comparison to "policy changes that took place coming out of the Great Depression".
"Therefore, it seems unlikely that US income concentration will fall much in the coming years."
Income counted in the analysis includes wages, private pension payments, dividends and capital gains from the sale of stocks and other assets, but it does not include unemployment benefits or federal public pension benefits, known as Social Security.
While the crash of 2007-09 adversely affected top earners, benefits of rising corporate profits and stock prices since then have largely gone to the richest, according to the study.
Incomes among the richest fell more than 36% between 2007-09, compared with a decrease of 11.6% for the rest of Americans. But in the last three years, 95% of all income gains have gone to the richest 1%.
The top 1% of American households had income above $394,000 (£250,000) last year. The top 10% had income exceeding $114,000.