WASHINGTON — Income for the richest Americans has grown 15 times faster than for the poor since 1979, a government study showed, as a poll out Wednesday highlighted deep anxiety over uneven wealth distribution a year ahead of US elections.

The income disparity, and concentration of more than 80 percent of US income wealth in the top 20 percent of earners, highlights the volatility in the race for the White House as President Barack Obama's Republican challengers push plans to reduce taxes for the wealthy as a way to prime the sluggish economy.

From 1979 to 2007, the wealthiest one percent of Americans more than doubled their share of the nation's income, from nearly eight percent to 17 percent, the non-partisan Congressional Budget Office said in a report released Tuesday.

"Income after transfers and federal taxes for households at the higher end of the income scale rose much more rapidly than income for households in the middle and at the lower end of the income scale," it said.

Government policy over the years has become less redistributive, and "the equalizing effect of transfers and taxes on household income was smaller in 2007 than it had been in 1979," the CBO added.

For the wealthiest one percent of the population, average after-tax household income grew by 275 percent during the period, compared with just 18 percent for the poorest 20 percent.

It was also a far greater increase than for the six tenths of the population in the middle of the income scale, who saw their average after-tax income grow by just under 40 percent during the same period.

Meanwhile a new poll by The New York Times and CBS News found that the vast majority of Americans fear a stagnation or deterioration of the economy, and showed that two thirds of the public believe US wealth should be distributed more evenly.

And in a critique of Obama as he attempts to position himself as the candidate best-placed to improve the status of the nation's working class, 28 percent of poll respondents said his policies favor the rich, compared with 23 percent saying they favor the middle class and 17 percent saying they favor the poor.

By contrast, 69 percent of respondents said Republican policies favor the rich, nine percent said they favor the middle class and two percent said they favor the poor.

The October 19-24 telephone poll of 1,650 adults had a three percent margin of error.