Born to Pay: THE NEW POLITICS OF AGING IN AMERICA by Phillip Longman(Houghton Mifflin: $17.95; 294 pp.)

The last thing the country needs is another special-interest group. But that is exactly what it is getting. The interest group is the baby-boom generation, the 77 million Americans born from 1946 to 1964. “Born to Pay” is an early salvo in a battle that is destined to rage for decades--the baby boomers’ battle with older and younger generations for a healthy and wealthy retirement.

Phillip Longman raises some critical issues while there is still time to address them. No one can question that the baby-boom generation in retirement will exert a tremendous strain on the American social and economic systems, just as it did when it went through the public schools and then entered the work force and the housing market.

But Longman, at 31 a card-carrying baby boomer, confronts the aging of his generation as a special-interest advocate. He is, although his book does not reveal it, the former research director of Americans for Generational Equity, a lobbying organization for the baby boomers. His analysis runs the risk of stampeding policy makers away from some of the very reforms that could help the baby boomers to a comfortable--if not wildly prosperous--retirement.

Today’s elderly, Longman observes, are the wealthiest ever; thanks to Social Security, their poverty rate is lower than for the rest of the population. Medicare has helped them enjoy their retirement years in good health.

Only in passing does he concede that the young have benefited as well. It bears emphasizing--and Longman does not emphasize it--that if Social Security has freed the old from dependence on their children, it has also lifted from the children the burden of supporting their parents.

From Longman’s perspective, however, the baby boomers are on the paying end of a fabulously generous retirement system. Like many of his generation, he fears that when the baby boomers are old enough to be on the receiving end, their sheer numbers will crush the system.

Birth rates fell precipitously after 1964, and, when today’s baby boomers are in retirement, they will have to rely heavily on the baby bust generation to support them. In 1985, there were 4.9 Americans of working age available to pay the taxes that support one retired American eligible for Social Security and Medicare. By 2030, when the last of the baby boomers will have reached 65, that ratio will have fallen as low as 2.2 to one.

Government policies, Longman argues, are conspiring with demographics to rob the baby-boom generation. Federal and local housing and zoning policies have driven up home costs, to the benefit of those who already own homes but the detriment of those who do not. The consumer ethic has drained money from investments in industrial expansion and education. Massive federal deficits will have to be repaid by future generations.

Longman would reverse these policies. And he would even try to stem the demographic squeeze on the baby boomers by encouraging more children. In today’s society, he argues, young children represent a financial burden for their parents, but thanks to Social Security and Medicare, grown children are no longer a vital source of support for their aging parents. No wonder so many couples have chosen to have smaller families or no children at all. Longman would increase government support for child care.

Longman’s proposal for restructuring Medicare is thought-provoking, although so politically explosive that it is probably a non-starter. Why, he wonders, should only the elderly be guaranteed government-subsidized health care? Treat everyone equally, he urges; that would bring to the United States a national health care service resembling Britain’s.

“In effect,” he says approvingly, “British citizens have traded access to heroic, costly treatments in their later years for an enhanced chance of becoming elderly in the first place.”

But when Longman turns to that biggest of all social insurance programs, Social Security, he is content mostly to fan baby boomers’ fears that the system will vanish before they are old enough to take advantage of it. Most authorities believe some prudent planning before the crunch comes--and the crunch is 25 years away--will guarantee Social Security’s future. Benefits will merely have to be somewhat less generous than now.

That’s not enough for Longman. By failing to concede that something has to give, he turns against some of the very measures that would help keep the system alive when the baby boomers are on the receiving end.

One would be to tax all of everyone’s Social Security benefits. If the elderly are to be treated like other members of society, why should their benefits be untaxed? Instead Longman opposes Congress’ halting first step in 1983 to tax half the benefits of recipients with high outside income. His self-interested argument: that the 1983 tax strikes at few of today’s elderly but will hit most baby boomers as inflation drives up their outside incomes.

Likewise, there is wisdom in pushing back the age at which the elderly become eligible for Social Security benefits. A man retiring at age 65 could expect to live 12 more years in 1940 but 19 more years today. Society cannot afford to support so many years of retirement, and baby boomers should not expect it. Yet Longman objects that the 1983 Social Security reform gradually pushes back the retirement age for full Social Security benefits to 67--a mere two years--for those retiring in 2027.

Longman despairs that economic growth will compensate for the trick that demographics has played on his generation. “Looking to the future,” he writes, “the continuing decline of the U.S. manufacturing sector, the massive trade deficits, and the low wages generally paid to workers in the growing service sector of the economy all argue against the possibility that today’s young workers as a whole will eventually become as upwardly mobile as were their parents in the 1950s and 1960s.”

That outlook rests on shaky premises. U.S. manufacturing is rebounding, and pay in the service sector is arguably as good as it is in manufacturing. More generally, such long-range forecasts are exercises in fortune telling.

Already, the nation has managed to absorb the baby boomers into the work force, defying the dire forecasts. Somehow the country will probably also manage to support the baby-boom generation in its retirement years.