Media playback is unsupported on your device Media caption Police fired tear gas to disperse protesters in Oakland, California

Income inequality in the US has sharply increased in recent decades, a bipartisan analysis has revealed.

The Congressional Budget Office said income had tripled for the richest 1% between 1979 and 2007.

Meanwhile, a major poll shows anxiety for the future is high, with a majority saying the US is "on the wrong track".

The findings emerged as police used tear gas and mass arrests to force Occupy Wall Street protesters out of their camps in Atlanta and Oakland.

Some 50 people were arrested in Atlanta and 85 were held overnight in Oakland, California.

After clashes in Oakland on Tuesday that left an Iraq war veteran in a critical condition, Mayor Jean Quan held a press conference on Wednesday to announce that the plaza would be open to protesting but not to camping.

Ms Quan said Oakland supported the protesters' goals, but had to act when a small number of them threw rocks, paint and bottles at the police.

Distrust of government

Many Occupy Wall Street protesters say they are making a stand against corporate greed and income inequality in the US.

Analysis The analysis from the CBO and the latest opinion poll are the backbone of a deeply unhappy narrative in America. For many people the link is broken between the idea of American capitalism - that hard work will be rewarded, that your children will have a better standard of living than you - and the reality of the system. Hard times have come and gone before. Incomes have been squeezed, and unemployment has been high. But the conjunction of events and attitudes is startling; economic insecurity, a vast and growing gap not just between rich and poor but between rich and middle class, and a sense of foreboding about the future, including deep distrust of the one body that people once looked to for solutions - the government. The CBO analysis is sobering, but the period under review ends before the 2008 financial crisis and the bitter recession that followed. Things have only got worse since 2007 for America's poor and its middle class. And right now it is hard to see when things will start to get better again.

As rallies continued, the report from the bipartisan Congressional Budget Office indicated the nation's highest earners saw their household income almost triple in the years between 1979 and 2007.

After tax income increased by 275% for the wealthiest 1% of Americans but by just 18% for the poorest 20%, the report said.

In addition, the report revealed that in 2005-2007, the years immediately preceding the financial crisis, the top 20% of the population earned more after-tax income than the entire bottom 80%.

Democratic House Representative Sander Levin said the findings confirm what Americans already knew.

"The rules have been changed by the unfair tax policies of the last decade and our tax code is doing less to level the playing field than it was in the past."

The poll, conducted by the New York Times and CBS News, shows distrust of government is at its highest level ever.

Almost half of those asked said they thought the sentiment behind the Occupy Wall Street protests reflected the views of most Americans.

Two-thirds said wealth should be more evenly distributed in the US.

Some 28% of respondents believe the policies of President Barack Obama favour the rich, although a strong majority - 69% - said that was the effect of Republican policies.

Baton rounds

The violence in Georgia and California comes as the Occupy Wall Street movement prepares to mark its sixth week of continuous protest.

Image caption 24-year old Iraqi war veteran Scott Olsen received a head injury

In the early hours of Wednesday morning police moved into Woodruff Park in Atlanta, Georgia, after issuing warnings that demonstrators should leave.

Around 50 protesters were arrested after midnight, as helicopters circled overhead and trained spotlights into the city square.

In Oakland, California, riot police used tear gas and baton rounds and made around 85 arrests to clear protesters from Frank Ogawa Plaza.

One protester, 24-year-old Iraq war veteran Scott Olsen, received a head injury from an object thrown during the demonstration on Tuesday. Doctors said he was in a critical condition.

Protest organisers said he had been hit by a tear gas canister, but this has not been confirmed.

Police Chief Howard Jordan told reporters at a press conference on Wednesday that an internal review board and local prosecutors would be asked to determine whether police at the scene had used excessive force.

Georgia State Senator Vincent Fort was among those arrested in Atlanta.

Referring to Atlanta Mayor Kasim Reed, he said: "He's using all these resources ... This is the most peaceful place in Georgia.

"At the urging of the business community, he's moving people out. Shame on him."

One protest organiser, Tim Franzen, said the city was facing a "crisis of priorities".

The mayor told the Associated Press news agency he was upset that a hip-hop concert with a crowd of 600 people was held over the weekend without a permit or security guards.

He said he also had security concerns after hearing reports that a man in the park was carrying an assault rifle.