Only one in three Americans believes they can every fully retire, according to a new survey. The 1000-person study, released by Scottrade, an online discount brokerage firm, found only 32 percent of Americans believe they will be able to permanently leave the workforce, down from 39 percent in 2008.

"Americans anticipate having to work longer, as their nest eggs have been shrinking and the economy has made it harder to save," Chris Moloney, Scottrade's chief marketing office, said in a statement.

According to Joseph Quinn, a professor of economics at Boston College, Americans have been working longer since the 1980s, when mandatory retirement and certain Social Security penalties were eliminated.

"All the demographic and social trends work in same direction: you can work longer if you want," he said.

But he expects the downturn will force people to take advantage of the opportunity to work longer.

Forty-three percent of respondents indicated their retirement accounts have decreased 10 percent or more since last year. Quinn predicts this hit will require retirees to return to the workforce, and others will delay when they leave.

"People will work longer and retire later, which was happening already, but this will make it more dramatic," he said.

But while 77 percent reported concern about social security's future and more than half think the money will run out before they retire, Quinn isn't concerned. Funding problems are another three decades away, and either moderately higher taxes or lower benefits would fix problems in the system, he says—it's just a matter of biting the bullet and making the changes.