TOKYO

AS POLICY wonks across the developed world fret about aging populations and overtaxed social welfare systems, America’s future has already arrived in Japan, where the labor force has started to shrink. The percentage of Japan’s residents over age 65 is closing in on 25 percent — a level that makes Florida seem youthful by comparison. But so far the country hasn’t declared bankruptcy or erupted in cataclysmic generational warfare.

Instead, its fate is partly in the hands of people like Kenji Ueda, a 72-year-old entrepreneur who founded a temporary employment service for older workers in Tokyo. Most of Japan’s elderly are healthy. So Ueda is giving them a chance to put their time to productive use — and trying, as he told me through an interpreter, to “strengthen the ‘elderly’ brand.’’

Such upbeat talk is oddly reassuring for the United States, now that yawning Medicare obligations are beginning to spook creditors and Social Security is paying out more than it’s taking in. For if Japan offers any guide, the graying of the population doesn’t just produce grim, abstract debates about how to divide up resources. It also raises a more interesting question: In a country where the elderly far outnumber children, and where retirement can last for decades, what does it take to live happily?

Ueda, who started his company after many years at Tokyo Gas, certainly means to make a profit for himself and his shareholders. But he also has higher goals: not just to give older workers an outlet for their energies, but even to alleviate the marital strains that develop when long-employed workers are suddenly home with their spouses.

That last part sounds like a joke, but it isn’t, really. Multiplied across millions of households, the search for harmony and happiness becomes an issue of national importance. In a series of interviews with policy experts, business people, service providers, and civic activists, the priority that kept coming up was ikigai, which translates as “life worth living.’’

“We have to develop a Japanese society,’’ said Akira Morita, director of a think tank at Tokyo University, “where the elderly can live with ikigai.’’ Attaining it is partly a matter of self-esteem: A senior citizens’ co-op named Koureikyo, for instance, is working to persuade Japan’s elderly that they are more than mere recipients of services.

A potentially thornier issue is what role elderly Japanese will play in the economic system. Many employers have a mandatory retirement age of 60 or 65. And while marketers have been calibrating their sales pitches to retirees for some time, there isn’t a clear path for those who want to stay in the workforce. Protections against age discrimination are weaker in Japan than under US law, and employers may underestimate their capacity to contribute. Ueda’s temp agency offers one option, at least for his roster of 370 workers, and he hopes others copy his business model.

On a broader scale, major employers are increasingly bringing back their retirees, often at reduced hours and lower pay. This isn’t a minor step: Especially in the hierarchical world of big Japanese corporations, it’s an adjustment for all when retired managers take direction from their former underlings, so some companies that “re-recruit’’ retirees make a habit of assigning them to divisions they have never worked in.

These patterns suggest a level of hard-headed realism. A 70-year-old is bound to have different needs and motivations than a 30- or 50-year-old.“We have to accept the fact that physical strength will decline,’’ said Morita, the think tank director. “Based on the fact of declining capacity, we have to enable these people to remain active.’’

Obviously, the public discussion of aging in Japan isn’t just about quality of life. Japan also faces the kind of policy choices that keep US deficit hawks up at night. The government is debating whether to raise a sales tax to pay for pensions. Japan’s stiff public debt, which ballooned amid the malaise of the 1990s, gives it less room to maneuver.

But that’s not the point. Japan’s experience shows that, while the aging of society looks mainly like a problem for the social-welfare system when it appears on the horizon, it reveals other dimensions when it arrives.

Objectively, it matters to society whether seniors feel useless and bored or needed and pleasantly occupied. People who say they have ikigai in their lives, studies show, have lower mortality rates than those who don’t.

Not all senior citizens need nursing care, and not all can take, or want to take, the equivalent of a permanent vacation in West Palm Beach. Over time, aging societies will have to recognize their older residents as an economic force and as a pool of talent — or as Ueda, the entrepreneur, sees it, as “a mountain of treasures.’’

Dante Ramos, the Globe’s deputy editorial page editor, reported this column on a fellowship through the Foreign Press Center of Japan.

© Copyright 2010 Globe Newspaper Company.