WASHINGTON — United Parcel Service is a model of corporate success its profitability anchored on the use of part-time workers. Each of the 12 million parcels and documents normally moved by UPS each day is handled on average by six part-time workers and three full-time employees. Of the 185,000 UPS workers represented by the Teamsters Union 60 percent are part-timers.

Now that employment strategy is under attack in a national strike where a key Teamsters demand is that UPS grant more workers full-time status.

The outcome of this struggle is likely to echo widely — slowing or accelerating one of the most significant corporate trends of the 1990s: the rapid growth in the use of part-timers.

Many companies will see it as a signal on how to shape employment policies in coming years.

“The reason people resonate on UPS is the general sense that nonstandard jobs are increasing that it is getting harder and harder to find a regular full-time job” said Eileen Appelbaum associate director of research at the labor-oriented Economic Policy Institute (EPI) in Washington.

“There are lots of people that want regular full-time employment but cannot get it. There are also lots of people in full-time jobs that are concerned that their employer might replace them with two part-time employees or a contractor or temporary worker.”

The use of part-time workers by American industry is growing. Part-timers made up about 16 percent of the national work force in 1975; now they are 18.5 percent or about 22 million workers according to the Bureau of Labor Statistics. They earn about 60 percent of the wages paid their full-time counterparts and EPI studies indicate that only about 15 percent of them are offered health care and 12 percent a pension.

Michael Kazin a professor of labor studies at American University in Washington said that companies have benefited financially from the expanding use of part-timers.

“You pay them less they don’t have the same stake in the company and most often they don’t organize” he said.

“Unions however have always been against part-time work. It’s easy to abuse the workers they have less control they have less of a stake in the industry and less reason to depend on the unions.”

But not every part-time worker wants or needs to work full-time said Carl Camden executive vice president for marketing at Kelly Services of Troy Mich. which specializes in finding temporary and part-time help for companies across the country.

Camden believes the use of part-timers is rooted in the global challenges faced by U.S. businesses and other fundamental changes in this country’s economy.

“To a degree the whole nature of work is dramatically changing” said Camden.

“You still have some institutions that think of work as a permanent job worked 40 hours a week from 9 to 5. But that is not the way the world is and is not the way the work force is” he said.

“Labor unions companies and government institutions will have to adjust to the fact that the nature of work has changed.”

UPS is a good example of a company that has grasped that vision.

To meet its customers’ demands for speedy movement of packages UPS uses the bulk of its part-timers to sort packages during four-hour time spans most often in the middle of the night.

Part-timers at UPS typically earn about $10.50 an hour while their full-time counterparts take home as much as $19.50 an hour.

UPS first negotiated part-timers into the Teamsters contract 35 years ago but up until 1982 paid them wages comparable to those of full-time workers.

In 1982 under considerable pressure to help the company which was being challenged by new delivery service rivals the Teamsters agreed to pay incoming part-timers less than incoming full-time employees.

The company claims the Teamsters are exaggerating the level of angst in its part-time ranks.

It says the majority of part-timers are college students or nontraditional employees who have no desire to take full-time work.

UPS spokesman Ken Sternad said the average part-timer at UPS earns as much as $11 an hour and that 60000 UPS part-timers earn at least $16,000 a year. They also get health coverage a retirement plan vacations and holidays.

According to Sternad some 13,000 UPS part-timers have moved into full-time jobs over the past four years and 8,000 new full-time jobs have been created.

“Most of the part-time workers at UPS are people who want to work part-time” he said. “Tens of thousands of our employees are students who are putting themselves through school with one of the best part-time jobs in America.”

Camden of Kelly Services agrees that the ranks of part-time workers are swelling in part because more people don’t want to work full-time.

“We have a significant number of people that don’t” he said. “They say they won’t take a full-time job. That’s one of the reasons they come to us. ”

Part-timers are often parents wanting more time with children early retirees who don’t want to go back to work full-time career changers who need experience in a new field but can’t afford to leave their old job behind and trailing spouses who follow their partner on each career move.

Another factor is the difficulty some companies have in finding full-time workers.

“An example would be the information-technology market” Camden said. “There are just not enough programmers right now. We have college kids and retirees working part-time in those jobs.

“If it were not for the part-time labor coming into that sector the gap between the employer needs and employee pool would be much greater than it already is.”

By Michael D. Towle, Knight Ridder Newspapers