Defined benefit pension plans have declined steadily, mostly replaced by 401(k)-type plans. known as defined contribution. There has also been little change in the percentage of employees not covered by either type of plan.

The death knell for the traditional company pension has been tolling for some time now. Companies in ailing industries like steel, airlines and auto parts have thrown themselves into bankruptcy and turned over their ruined pension plans to the federal government.
More Companies Ending Promises for Retirement – New York Times