Fred Hemmings figures he’s spent a lifetime on the vanguard of rising opportunity and crashing change.

A champion surfer, he joined with Randy Rarick to found the first professional surfing tour. And while his endeavors as a Republican state legislator were often stymied, he nonetheless led the way in numerous efforts to reform government, promote business and protect the environment.

But in less than two months, Hemmings will find himself at the leading edge of a decidedly different type of movement as the largest-ever generation of Americans begins an adventure of unimaginable proportion and consequence: old age.

Hemmings was born on Jan. 6, 1946, placing him among the first of the baby boom generation. When he and his fellow 1946 babies begin turning 65 next year, it will mark the beginning of a dramatic demographic shift in the United States, and particularly in Hawaii, which already has an above-average number of older residents per capita.

The change is perhaps the biggest yet for a generation used to major cultural, technological and political shifts.

"My life is punctuated by the greatest and most rapid evolution of humankind since the dawn of civilization," said Hemmings. "That’s a bold statement but it’s validated by historical fact. We went from flying machines to exploring the farthest reaches of space. We’ve conquered many diseases, including polio, which I suffered as a child. And our technology is advancing so rapidly that it’s obsolete the moment we get it in our hands."

Even so, the generation that defined youth culture in America faces an uncertain future as it reaches a very different sort of seniority than its predecessors.

Baby boomers are generally defined as those born between 1946 and 1964 and number about 80 million in the United States. In contrast, the preceding generation, popularly referred to as the Traditionalists (1925-45), numbered just 44 million, and Generation X (1965-1980), about 46 million.

From now until the last of the baby boomers reaches age 65 in 2030, the U.S. senior population is expected to increase from 12 percent to 19 percent of the total U.S. population, thereby increasing the burden on a smaller population of working-age Gen-Xers and Millennials (those born between 1981 and 2006) to bear the cost of caring for aging boomers who may no longer be contributing to the tax base.

The shift in Hawaii could be even more onerous as the local senior population balloons from 15 percent of all state residents this year to 23 percent in 2030, according to the state Department of Business Economic Development and Tourism.

To date, most of the focus has fallen on the potential effects of this massive "aging-up" on the health care system and the overall economy.

Medical and nursing organizations have long sought to address what is anticipated to be serious staffing shortages through a variety of approaches, including radically redesigned delivery systems. Yet questions remain about the ability of existing hospitals and care facilities to accommodate a population that is not only larger than any previous generation, but also likely to live decades beyond retirement because of advanced medical technology.

The cost of maintaining entitlement programs like Medicare and Medicaid is another immediate concern.

Through the next 20 years, federal spending will need to increase significantly to accommodate the number of Americans age 65 or older. For example, Medicare spending would need to increase from 3.7 percent this year to 8.7 percent by 2030 to meet expected demands, according to Georgetown University’s Center on an Aging Society.

Likewise, while estimates vary on when the increase in Social Security-eligible citizens will reach crisis levels — a 2009 report prepared by the Social Security and Medicare Board of Trustees estimates that Social Security will start paying out more than it collects within the next seven years — most agree that the system will eventually fail unless significant changes, either in funding or in benefit offerings, are not made soon.

The breadth of concern overlaps nearly every aspect of civic and personal life.

Will boomers and Millennials (who number 78 million) compete for limited public resources, pitting issues like long-term care against education?

Will the government relax immigration laws to allow young immigrants to fill necessary jobs and shore up the tax base?

Will a mass withdrawal from the housing market lead to much more supply than demand, as University of Southern California researchers recently suggested?

How will Hawaii’s public spaces have to adjust to meet the changing needs — longer traffic lights, larger street signs, wider sidewalks — of its older folks? And where will the money come from?

How will industries fill the experience gap when highly skilled older workers exit the working world? If boomers are willing and able to work past traditional retirement age, what types of workplace accommodations will they expect?

And how will Hawaii families absorb the financial and personal responsibilities of caring for the longest-living seniors in the nation?

While the graying of the boomers and its attendant wave of social, political and economic complication was certainly foreseeable, it has also been immensely difficult to deal with.

While some blame shortsightedness, lack of economic resources or failure of political will for the relative absence of preparation, experts concede that the already unprecedented shift in demographics has been further complicated by the unique and unpredictable nature of the baby boomers themselves.

While attempting to identify the common characteristics of a population of 80 million might seem like a perilous endeavor, sociologists have been able to isolate a few telling traits.

As the commercial marketplace has understood for decades, baby boomers are averse to the traditional markers of getting old and have been willing over the course of their adult lives to spend liberally on products and services that help them to maintain an appearance of youth and on experiences associated with an active, engaged lifestyle.

Boomers also value their independence and are more likely to favor assisted-living arrangements versus traditional nursing homes.

Boomers have enjoyed a higher standard of living than previous generations and have been more willing to depart from traditional familial and social structures.

As the state Executive Office on Aging noted in its report "Baby Boomer Data: 2000," boomers have married later, had fewer children and been more likely to enter new relationships. They also tend to spend more than they save and expect to rely at least partially on entitlement programs to survive their old age.

According to the report, Hawaii boomers are not likely to have graduated college (only 27 percent did) or own a home (only 41 percent did as of 2000). In addition, only 42 percent have been saving for retirement. While generally healthy, they are nonetheless also more likely to smoke, drink and be overweight than their parents.

In comparison with boomers on the mainland, local boomers are likely to live longer, have more formal education, have fewer children, have higher incidences of divorce and remarriage, and have a higher median family income.

Yet, those who have closely studied the generation warn that such profiling has only limited value in predicting how boomers will act as they reach their senior years.

"It is dangerous to extrapolate on existing trends or assumptions regarding boomers because they are much more likely than any other generation to significantly change their lifestyle," said Jim Dator, a University of Hawaii professor of political studies and director of the Hawaii Research Center for Futures Studies.

"Boomers who grew up in the 1960s and ’70s differed more from the previous generation in terms of lifestyle, technology and attitude than any generation before them," Dator said. "They love fads, and they are quick to change established habits. Therefore, you can’t predict their future behavior based on their past behavior."

True to elusive type, Hemmings said his own life has been marked by "perpetual reinvention of self."

"I never had a career," he said. "I just followed my dreams."

Indeed, without benefit of a college degree, Hemmings followed a unique path to success in athletics, entrepreneurship and politics, along the way making the necessary adaptations to what he considers the most dynamic period of change in history.

Carlos Barientos III, 45, was too young to take in many of the generation-defining moments of the ’60s and ’70s — the moon landing, the Vietnam conflict, the civil rights movement — but he takes pride in upholding the sense of passion and idealism that characterizes his cohort.

Barientos was born in Honolulu shortly before 7 p.m. on Dec. 31, 1964, among perhaps the last baby boomers born in the United States.

"The ones who came before went through some nation-changing events," said Barientos, a musician and soon-to-be small-business owner. "They stood up and fought for a lot of the core values we hold today. I kind of missed the reality of all of that, but I feel fortunate in that I sort of have the best of both worlds: the vision and viewpoint of the older (baby boomers) and the ongoing experiences of the world that is still rapidly changing."

Like Hemmings, Barientos marvels at the changes he’s seen in just the first half of his life.

"I remember listening to eight-tracks in my uncle’s car, and now I build websites for a hobby," he said. "But the pace of change wasn’t as fast as it is now. I remember when I got a double-cassette boom box. I thought that was the ultimate. I thought technology was finished after that.

"This new generation is used to a much faster rate of change," he said. "They’re change-numb."

Barientos shares much in common with older boomers. Following his own interests and desires, he’s changed jobs a few times and has no reservation about starting a new business venture in midlife. He also waited to become a parent; daughter Phoebe is just 5 years old.

And while Barientos prefers not to speculate about what life will be like when the boomers finally take their place as the elders of American society, he says he hopes that America’s largest generation will leave a legacy of positive change worthy of all the fuss.