CHICAGO — When Baxter International Inc.'s shareholders asked tough questions about pension financing last year, they got an unequivocal answer.

Baxter's pensions are "sacred," Chief Executive Officer Robert Parkinson said at the annual meeting in May.

But traditional pensions are not sacrosanct in an age where more companies — including big ones with well-financed plans — are shifting the risk of saving for retirement onto workers.

The pension freeze announced this week by IBM Corp. will make it easier for large employers to stop offering plans that promise payments for life, experts said yesterday. And it will hasten the shift to plans such as 401(k) savings accounts, which provide no such guarantees.

"Now that a large well-funded sponsor did it, it may be that some of these other sponsors won't consider it a third rail that they can't touch," said Temple University professor Jack Vanderhei, who directs a research program for the Employee Benefit Research Institute.

IBM froze its pension plan for U.S. employees, one of the nation's biggest with more than $48 billion in assets, which had more than enough assets at the end of 2005 to meet its future obligations, the company said.

The freeze will not affect the company's 125,000 retirees. But about 120,000 active employees no longer will earn additional benefits after 2007. Instead, they will receive larger payments to their 401(k) accounts.

The action drew sharp criticism yesterday from union leaders and employee rights groups.

"We're not looking at situations like with the steel companies and the airlines where these industries had been deeply troubled and had to enter bankruptcy to save themselves," said John Hotz, of the Washington, D.C.-based Pension Rights Center.

Traditional pensions, known as defined benefit plans, cover an increasingly smaller slice of the workforce, even though about two-thirds of the nation's Fortune 1000 companies still offer them, studies show.

The percentage of private sector employees with defined benefit pensions has fallen from 35 percent in 1980 to less than 20 percent now, according to the Employee Benefit Research Institute. About 21 million full-time private sector workers were covered by traditional pensions in 2003, the latest year for which data was available. About 43 million were covered by so-called defined contribution plans such as 401(k) accounts.

Plan freezes are increasingly common as companies try to limit the unpredictability of traditional pension plans where the value of assets can swing wildly from year to year, pension experts said. Stricter accounting rules and pending federal legislation are expected to increase the volatility.