WASHINGTON (June 20) - Sixteen-year-old Ryan Graham's mother is white. His father is black and according to census data, a significant share of the America's multiracial population is young like him.

The number of people who identified themselves with two or more races was relatively small when compared to other race categories. Yet 2000 census data shows this group tends to be more youthful, suggesting that they could play a prominent role in shaping the nation's demographics in the coming decades.

For instance, in at least 10 states, the percentage of multiracial residents who are of school age - between 5 and 17 - is at least 25 percent.

That is higher than for Americans as a whole, regardless of racial background. Nationally, 19 percent are school age.

"The reason we are in existence is so that we can put ourselves out of existence," Katherine Kiley, said of the group she helped start, the New England Alliance of Multiracial Families.

Kiley, of Natick, Mass. is white, and she adopted an 11-year daughter who is black and white and 10-year-old twin boys who are black. "We are hoping the growing numbers means people won't rely on groups like ours anymore," Kiley said.

Society grew more accepting of interracial relationships and families during the 1990s, said Dowell Myers, professor of urban demography at the University of Southern California. The 2000 census was the first to give people the option of checking off more than one race.

As multiracial youths grow older and start their own families, expect the racial portrait of America to become even more complex in future censuses, Myers said.

The figures are the first detailed age breakdowns by race and ethnicity. They are part of the latest state-by-state release of detailed data covering topics asked on all census forms.

Eight states and the District of Columbia received their numbers Wednesday. Ten states now have the data, with all 50 expected to get them by August.

Until now, the Census Bureau only released national and state figures for those 18 and older, and under 18.

Nationally, just over 2 percent, or 6.8 million of the country's 281.4 million people, identified with more than one race. Of the 6.8 million, 42 percent, or about 2.9 million, were under 18.

More specific national breakdowns by age and race - such as how many kids across the country are multiracial and school-age - will not be available until August.

But a look at state data released so far offers some clues:

-Of Nebraska's 1.7 million residents, about 19 percent were between age 5 and 17 in 2000. But of the 24,000 in Nebraska who chose two or more races, 34 percent were school age.

-Illinois had one of the largest multiracial populations in the country at just over 235,000, with 15 percent under age 5. By comparison, about 12 percent of the state's Hispanics were that young, and 6 percent of non-Hispanic whites.

"Hispanic" is considered an ethnicity, not a race; therefore, people of Hispanic ethnicity can be of any race.

The 1990 census allowed Americans to choose only one of five race categories. The 2000 count was the first to let people choose more than one category, increasing the number of race classifications to 63.

What multiracial Americans today take away from the historic new reporting of their population will affect the trends that emerge in the 2010 census. For instance, how will children identified by their parents today as multiracial classify themselves in the next head count?

Multiracial kids encounter "a lot of pain and isolation" in schools and social settings, but the situation improved during the 1990s, Kiley said.

Others talk about problems with parents who are wary of their kids getting into interracial romances, said Graham, a high school senior from Tallahassee, Fla., who runs "Teen Project RACE," a teen support group for multiracial issues.

Graham's family actually did not answer the race question on the census form. They lobbied for a box that allowed people to check off "multiracial" as a response, saying it would offer the most accurate picture of that population, rather than having people check off specific race combinations.