WASHINGTON — The elderly population in the United States could nearly double in size over the next quarter-century as baby boomers reach retirement age.

But the "aging crisis" in America will not be as severe as in other industrialized nations, the Census Bureau says in a report released Tuesday.

The 65-and-over population in the United States could increase nearly 80 percent by 2025, but there will be just 15 percent more working-age adults and 15 percent more children younger than 15, according to bureau demographers.

More senior citizens will be dependent on Social Security and Medicare, but fewer workers will be contributing to the publicly funded programs. It is a scenario lawmakers have long been considering in trying to guarantee the solvency of Social Security for future generations.

If the current system is not changed, Social Security is expected to start paying more in benefits than it collects from payroll taxes by 2016.

Still, other countries classified by the bureau as "more developed" — as the United States is — have more difficult demographics to deal with, the report said. Other "more developed" countries are expected to have a 46 percent surge in elderly population by 2025 but will also see declines in working-age population (by 7 percent) and the number of children (17 percent).

"If present trends continue, the impact of population aging is likely to be less severe in the United States than in other more developed countries" where immigration and fertility rates are lower, the Census Bureau report said.

"Less developed" countries will see their 65-plus population grow by 130 percent, with a 44 percent increase in working-age population and 5 percent surge in children.

"The under-5 population is becoming a scarce resource," said Dr. Richard Suzman, an associate director at the National Institute on Aging. "In the long term, maybe it becomes more important to invest in children's education to increase their earnings potential over their lifetime."

Only China and India have larger populations than the United States' 281 million. The United States is second behind China in the number of people 80 and older, and has the sixth-largest population of children 5 and younger, behind India, China, Indonesia, Nigeria and Pakistan.

Left unclear is how dependent retiring baby boomers will be on programs like Social Security and Medicare. Generally, Americans are living longer, healthier lives, and some surveys show that many soon-to-be seniors plan to work past retirement age.

"What are baby boomers going to do? That's the big question," said John Haaga, a demographer with the Population Reference Bureau, a nonprofit research group. "Are a lot of these 65-and-overs still going to be active and working and not really dependent at all?"

Census 2000 found 35 million people 65 and older, with 9.2 million 80 and older. Over 60 million Americans were younger than 15, and 19.2 million younger than 5. Over 186 million people were between 15 and 64, considered to be working age.

A comparison of the young and old

Top 10 countries in population under age 5, and 80 or over, in 2000, according to the Census Bureau.

Under age 5:

India, 116.8 million

China, 99.6 million

Indonesia, 24.1 million

Nigeria, 20.9 million

Pakistan, 20.5 million

United States, 19.2 million

Brazil, 16.5 million

Bangladesh, 14.6 million

Ethiopia, 11.8 million

Mexico, 11.4 million

80 and older:

China, 11.8 million

United States, 9.2 million

India, 6.1 million

Japan, 4.6 million

Russia, 3.0 million

Germany, 2.9 million

United Kingdom, 2.4 million

Italy, 2.3 million

France, 2.2 million

Spain, 1.5 million

Associated Press