When baby boomers begin to gray their way into the "grandma boom" around 2011, a smaller proportion of adult workers are going to have to find a way to care for them, according to a division chief for the U.S. Census Bureau.

"America is in transition as an aging society," said Cynthia Taeuber, chief of the age and statistics branch, population division, of the bureau."In the U.S. in 1900, 3 million people were over 65. In 1980, it was 30 million, or one in eight Americans. But during the baby boom, from 1946-1964, 70 percent more people were born than in the preceding two decades. Boomers represent one-third of the total population. And in 2011, they will begin to turn 65."

If birth rates remain about the same, these retirees will account for 20 percent of the population. By 2050, more than half of Americans will be over 50. The cost in federal dollars, she said, could be astronomical.

America is not the only country experiencing this growth, which is a worldwide trend. China now has 60 million-plus over 65, while Sweden has the highest proportion with 17 percent of its population over the age of 65.

The biggest change results from fertility rates and life expectancy. Mortality rates, especially among women and the "oldest old" - those 80 or older - are dropping sharply, mainly because of reductions in heart disease, cancer and stroke.

So the Census Bureau has made what Taeuber calls a "series of middle assumptions" about the future and what Americans should start planning for, while boomers are in their most productive years.

With the reduction in mortality rates comes the assumption that people are healthier, which Taeuber said is a little misleading. "Men tend to have lethal illnesses. Women tend to have chronic illnesses," she said.

Right now, of those age 65-74, two-thirds report good or excellent health. One in nine report they can't do physical activities. Of those over 85, only one in four are in institutions. Of the three-quarters who live at home, 20 percent have limited ability and need outside help.

"That's the health situation of the oldest of the old, and it varies greatly with the individual," Taeuber said, "so it really doesn't make sense to talk about `the elderly."'

Older men are more likely than older women to be in family setting, and older couples have more money than those who live alone, statistically.

"Older men are less likely to be in the labor force now," she said. "More of them take retirement options. After retirement, income levels are lower and less secure, but there's been significant improvement since 1970."

When people reach their 80s, their assets generally stop increasing. But today's elderly lived through the Depression and save well, while potential grandma boomers don't save and will suffer for it later if they don't change their style of spending, especially since a large percentage of senior citizens rely on Social Security benefits to live.

"The growth of the older population is a virtual certainty," Taeuber said. "We are entering the age of age. And more older people are living to be old enough to have multiple illnesses.

"Family structures are odd, too. With so many step-families and broken families, more and more elderly are having to care for themselves.