ALEXANDRIA, Va. – Most Americans don't plan to or can't quit working at a certain age and pursue a life of leisure. The Towers Perrin Retirement Study: Redefining Retirement in the 21st Century, concluded that changing expectations and pressures are reshaping the retirement landscape in the United States for employers and employees. Some expect to shift into new careers and continue to be productive, no longer thinking of retirement as a distinct phase of life, according to the study. More than three-fourths plan to work past traditional retirement age. Sixty-four percent of these employees expect to continue in part-time jobs, and 57% plan to change occupations. The study found that most employees don't expect company and government retirement programs to promise lifetime financial security, the study stated. However, it said workers are deeply concerned about pensions and health care insurance in their later years and are unsure how much money they will need in their 60s, 70s and beyond. Ninety-three percent of employers responding to the survey said that employees need to take on more responsibility for their retirement, but 76% said they have a continuing obligation to help finance employees' retirement. The study also found that companies are continuing to shift from traditional defined benefit pensions to defined contribution and hybrid plans. Forty-one percent of employers polled said they had converted a traditional pension to a cash-balance plan, a controversial practice that has been challenged in courtrooms and debated by federal lawmakers and regulators.