Mercer said 75 percent of the 400 mid-size and large firms it surveyed pay severance, but what a departing employee receives is often based on job ranking. Seventy-four percent of employers provide continuation of benefits to executives, but only 61 percent do the same for nonunion, hourly workers. Sixty-nine percent offer outplacement services to executives, compared to 49 percent for clerical or technical staffers.

Seventy percent of those surveyed said they have no plans to modify their current severance policies, Mercer said.

"Although most companies have taken a variety of initiatives to trim workforce costs, their severance policies have remained unchanged," said Steve Gross, global leader for Mercer's performance-and-rewards consulting business. "Severance pay helps preserve the future goodwill of employees, which can be a difficult investment to measure over the short term."

Of the respondents, 52 percent said they don't have a minimum-length-of-service requirement for paying severance.

Mercer, a subsidiary of Marsh & McLennan Cos. Inc., has more than 18,000 employees in 40 countries and territories.