A fundamental change is beginning to emerge in the way employe benefits, particularly medical insurance, are structured at some American companies. The change will mean higher costs for traditional families and lower costs for singles and two-earner couples.

The new system is called "equal benefits for equal pay."

It is based on the argument that people earning comparable wages are entitled to receive the same amount of money from their employers for medical or dental coverage, regardless of their family size. Simply put, an employe who happens to have dependents should not derive more from the company than the single worker making a similar contribution to its productivity, according to this reasoning.

The arrangement favors the average worker who is today apt to be unmarried, a single parent or a member of a two-income household. For the employe with a nonworking spouse and several dependent children, it means greater costs for the same amount of insurance because this employe's premiums no longer will be subsidized by colleagues who need less coverage.

Equal benefits for equal pay is still unusual and is very controversial. Opposed by organized labor, which sees it as a form of give-back, benefits "equality" is most popular with new, small or nonunion service companies.

Union Mutual Life Insurance Co. of Portland, Maine, reports that about 5 percent of its clients are moving in this direction. Hewitt Associates, an international management consulting firm, estimates that fewer than one-third of the employers who have instituted flexible compensation programs, or "cafeteria plans," eliminate family subsidies altogether.

To date, health-care groups, banks and universities -- which employ more women proportionately -- have shown the most interest, according to Hewett. Bankers Trust Co. and several other large banks have had benefits equality for years. Other U.S. corporations that have begun phasing it in include American Can Co., Nynex and Comsat.

Most benefits programs hark back to the days when the nuclear family dominated and the costs of care were reasonable. During the days of the Great Society programs of the Johnson administration, bigger and better benefits became a corporate byword. High inflation and high taxation transformed benefits, which were originally a form of protection, into a form of compensation. But today, both families and economics have changed.

The rationale for benefits equity, according to Hewitt, is that "people are paid according to the task they perform, irrespective of their family status. Benefits equal additional compensation, so if an employer does not 'pay more' because an employe has dependents, why should greater benefit value be provided because of an employe's family circumstances?"

Lance D. Tane, who is with the Washington office of Wyatt Co., a management consulting firm, disagrees strongly with Hewitt and contends that elimination of family subsidies has little to do with philosophy and much to do with economics.

Benefits now average 37 percent of manpower costs, according to Wyatt. In addition, companies complain that employes fail to appreciate benefits they've come to expect "free," and that the advantage of group purchasing of health insurance is disappearing as employes gain access to low-cost health maintenance organizations.

"What we're seeing here is the trend back to making these insurance plans protection against catastrophic loss and having individual employes pay for their own ordinary coverage," said Tane.

He cited a Wyatt study showing that, whereas in 1978, 54 percent of employers surveyed required no employe contributions to medical plans, only 38 percent required none in 1984. Coverage for self and family required a contribution by one-quarter of employes in 1978; four years later, 41 percent contributed.

Wyatt likens the trend in medical coverage to that in pension plans: away from defined benefits, which guarantee a certain level of benefit, toward defined contributions, where the employe and company contribute a certain amount without any guarantee of how large the final benefit will be. In other words, the the risk is shifted from employer to employe.

This shift in responsibility for health coverage is increasingly accompanied by more involvement of employes in choosing the type of insurance they want through cafeteria plans. Just over 10 percent of companies with more than 100 employes now offer their workers a "menu" of health, thrift and other benefits such as child care, according to the Employers Council on Flexible Compensation's survey of 600 companies.

The idea is that people not only will select coverage suited to their needs and thereby reduce duplication, but will also become more cost-conscious. B. F. Goodrich Co., for example, recently announced that it cut medical costs -- which had been rising at 20 percent annually -- by 0.5 percent last year by rewarding workers who curb their own bills.

Flexible-benefits programs save money, but eliminating family subsidies is just another way of dividing the same amount of benefits. So a company must make a policy decision whether it wishes to eliminate subsidies.

In a company that pays all benefits without asking for employe contributions, family subsidies are not readily visible to employes. But when employes are allotted tax-free dollars or credits that they can "spend" on selected benefits, subsidies are more obvious.

Flexible-benefits programs, by their nature, oblige companies to allot a given amount per employe. For example, a corporation may find that its health-care costs are $1,000 per employe. Traditional family coverage costs $3,000.

To establish true parity, the company could continue to pay the $3,000 family coverage and give back $2,000 to the single worker, or reduce the amount allotted for both single workers and employes with dependents to $1,500. In that case, because the actual cost to the company per single person remains $1,000, that person would get a $500 refund while the employe with dependents would contribute $1,500 to the plan.

Electives soften these hard financial realities. Instead of a taxable refund, the single person can elect additional benefits, such as disability insurance or a contribution to the thrift plan. The family person can take a plan with a higher deductible or give up some vacation days.

While parity appears to benefit singles at the expense of the family, often it also benefits a two-earner family. If an employe's working spouse is covered by another company with a traditional plan, the other employe can choose the cheaper, single coverage -- or, in some cases, no coverage -- from his own company.

When a company decides to eliminate family subsidies, it often will phase in parity over several years to avoid culture shock.

At Nynex, benefits administrator Peter Goodale said management has set a five- to six-year timetable for nonunion employes to reach parity. "It's one of many cultural changes going on, getting us away from paternalism and making us the lean, mean competitive company we want to be," he said.

Al Cassesse, director of corporate benefits for American Can, explained, "We are three-quarters of the way there." But he admitted that both single and married employes had complained. Singles got more credits at higher cost, while marrieds got lower credits at lower cost. "We met in the middle," he said. "But it's a no-win situation; nothing makes it totally equal."

Sometimes it proves too controversial. Patricia Dempster, a benefits specialist with TRW Inc. in Redondo Beach, Calif., reported that the company was charging employes with dependents more for health insurance. But when some of them grumbled, the company "retracted a bit," she added.

Frederick Rauh & Co., a Cincinnati insurance brokerage, moved to parity 12 years ago. "We thought we owed an obligation to employes," said David Eslich, manager of employe benefits. Most of Rauh's 62 employes are single or have working spouses, so its family plan costs employes 120 percent more than single coverage, while coverage for an employe plus one dependent costs 30 percent more than single coverage.

In June 1984, Valero Energy Corp. in San Antonio instituted a five-year phase-in of parity. In the first year, the cost of coverage ranged from $1,192.50 for a single employe to $1,994.50 for dependents coverage. In the fifth year, the cost for each employe will be $1,325 in constant dollars. Consequently, singles will get a rebate of $133 and the dependent program will cost $669 a year more.

Valero invites a single employe to buy more vacation time with the rebate, get extra dental or medical benefits or enrich a savings plan. An employe with dependents can sell vacation time, take the highest deductible, or have less life insurance as an alternative to making a cash payment to the company.

W. W. Richardson III, manager of employe benefits, said that Valero had no increase in health-care costs in 1985. As for fairness, he said opposition from employes with families dissolved in the second year. "Some companies juggle figures to keep on subsidizing families," said Richardson. "But employes are not dumb. We were concerned with having a credibility problem if we did that."