It's not hard to understand why people decide to switch careers when they lose their jobs. Being shown the door, for whatever reason, convinces them they have no future in their area of expertise.

But they should resist the temptation, according to the company that created "outplacement" the corporate practice of helping discharged employees find new jobs.In a survey of the nation's largest corporations, Challenger, Gray & Christmas found clear evidence that changing fields is a major mistake because companies want experienced people.

"Those who change careers become `throw away' workers who are discarding their own futures," said James E. Challenger, president of the Chicago-based firm that conducted the poll of Fortune 500 companies.

"There is no way a career changer can possibly compete for the same or better salary in the new function even with workers who have only a few years of experience."

He said the survey shows that 60 percent of personnel officers rank experience as their top priority in hiring.

Career changers, said Challenger, can't come close to holding salary, even if he or she is accepted for a position in a new industry. The newcomers can expect an average loss of 20 to 50 percent of their former income in the new job.

"Our studies show that it takes an average of five to 10 years to get back to the former salary level after changing careers," said Challenger. "The more years that are invested in a career, the longer it takes to equal the former salary in the new career."

The survey indicated that the majority of career changers tend to be under age 45, an indication that impatience may be one of the main reasons for the switch. Older workers tend to be more stable and remain within the field of their primary experience.

Challenger said the impetus for managers to change careers often comes from the way the discharge process works.

"If there is one thing in common that discharged people have, it is shock. Many believed they had total job security and were immune to such factors as mergers, sellouts, closures or layoffs. In the aftershock, some decide that it is better to start over in a new field."

But Challenger said that, for those who know how to look, job opportunities will still exist in their major field of experience no matter how bleak the outlook seems.

Rather than starting from scratch in trying to make contacts in a new function, Challenger advises job seekers to concentrate on their expertise to identify new job opportunities.

"A salesman is a salesman and he or she is not going to be hired as a plant superintendent over people who have been in manufacturing more than 10 years," he said.

The person who does move to another field can expect to be outclassed by the more experienced competition, he said. Even with a job in that field, the combination of having less income and less on-the-job status is likely to be a source of discontent over the long run which will adversely affect job performance.