U.S. workers age 50 and over expect to work longer, but many say they expect to never retire, according to a new survey by the the Employee Benefit Research Institute (EBRI).

The EBRI study examines data from the University of Michigan's Health and Retirement Survey on how the expected retirement ages of older Americans changed during 2006 to 2010, covering the periods before, during and after the recent recession.

In 2008, during the recession, 22.4% of workers age 50 or over said they plan to never retire. That declined to 16.3% in 2010. Over the 2006-2010 period, another 14% to 18% of workers said they don't know when they will retire.

"The general trend shows that older Americans are expecting to retire later," said Sudipto Banerjee, EBRI research associate and author of the study. "But the most striking finding is that nearly 20% of the sample expects never to stop working and more than 15% of the sample don't know when they are going to retire."

In 2006, about 11.2% of workers age 50 or over expected to wait to age 70 before retiring. By 2010, after the recession had ended, the number of workers who expect to retire at 70 jumped to 14.8%. Even at higher ages, the expected retirement age has jumped. Just 1.7% of workers age 50 or over planned to retire at age 80 in 2006, while that has more than tripled to 5.2% in 2010, according to the study.

The study also found that the expected retirement at the ages of 62 and 65 also steadily declined over the four-year period.

The EBRI report also noted that the rising age of expected retirement may reflect a growing awareness of economic and fiscal reality among Americans workers, especially at a time of rising longevity. At the same time, the organization noted that many workers may not be able to work as long as they would like. The 2011 Retirement Confidence Survey found that 45% of retirees leave the work force earlier than planned.