The biggest retirement plan trend in recent years—the shift by employers away from defined benefit plans—may start to ease, a survey suggests.

As recently as 2000, more than 90% of large employers offered defined benefit plans to new employees, according to a Towers Watson & Co. survey of 424 employers, mostly Fortune 1000 companies.

But following a surge of pension plan freezes starting around 2004, only 36% of those employers now offer defined benefit plans to new employees, according to the Towers Watson survey released last week. By contrast, nearly two-thirds of those employers now offer only defined contribution plans to new employees (see chart).

In the past 12 months alone, well-known employers such as Bank of America Corp. and General Motors Co. have announced pension plan freezes for salaried employees.

There are several reasons why employers have moved away from defined benefit plans, including—most recently—mandated low interest rates that employers must use to value plan liabilities. That has fueled increases in plan liabilities, forcing employers to significantly increase contributions to their plans.

“With low interest rates, there has been more of a financial burden on employers to offer defined benefit plans,” said Alan Glickstein, a Towers Watson senior retirement consultant in Dallas.

But employers' shift away from defined benefit plans may slow in the years ahead, the Towers Watson survey suggests. Of the 36% of employers that still offer defined benefit plans to new employees, 68% said they remain committed to offering them over the next two to three years.

More than 70% of employers cited employee attraction and retention as the key reasons why they intend to continue to offer defined benefit plans to new employees.

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Indeed, attracting and retaining employees will assume greater importance in the years ahead as the baby boom generation retires and the pool of available employees shrinks.

“Keeping a defined benefit plan could make an employer a little more attractive and better able to keep employees they critically need,” Mr. Glickstein said.

Still, most employers that have closed or frozen their defined benefit plans are not likely to reopen them. Seventy-one percent of employers with frozen plans said their decision to freeze their plans is final, while 57% of respondents with closed plans said their decision is final, according to the survey.

In a pension plan freeze, new employees are not allowed to join the plan, while current participants do not accrue future benefits. In a plan closure, some or all current participants continue to accrue benefits, but new employees cannot join the plan.

The survey also found that employers have moved away from traditional defined benefit plans more rapidly than hybrid plans, which typically are cash balance plans.

For example, in 2004, 240 respondents offered a traditional defined benefit plan, while 115 sponsored a hybrid plan. In 2008, 132 employers offered a traditional plan compared with the 104 who offered a hybrid plan.

But this year, 82 offered a hybrid plan compared with just 70 employers that offered a traditional plan to new hires. The remaining 272 respondents only offered defined contribution plans to new employees.

Cash balance plans have enjoyed a mild resurgence in the wake of a 2006 law that made clear that the basic design of the plans does not violate age discrimination law.

Since then, several large well-known employers, including The Coca Cola Co., Dow Chemical Co. and MeadWestvaco Corp., have adopted cash balance plans.