Children now make up less of America's population than ever before, even with a boost from immigrant families.
And when this generation grows up, it will become a shrinking work force that will have to support the nation's expanding elderly population _ even as the government strains to cut spending for health care, pensions and much else.
The latest 2010 census data show that children of immigrants make up one in four people under 18, and are now the fastest-growing segment of the nation's youth, an indication that both legal and illegal immigrants as well as minority births are lifting the nation's population.
Currently, the share of children in the U.S. is 24 percent, falling below the previous low of 26 percent of 1990. The share is projected to slip further, to 23 percent by 2050, even as the percentage of people 65 and older is expected to jump from 13 percent today to roughly 20 percent by 2050 due to the aging of baby boomers and beyond.
In 1900, the share of children reached as high as 40 percent, compared to a much smaller 4 percent share for seniors 65 and older. The percentage of children in subsequent decades held above 30 percent until 1980, when it fell to 28 percent amid declining birth rates, mostly among whites.
"There are important implications for the future of the U.S. because the increasing costs of providing for an older population may reduce the public resources that go to children," said William P. O'Hare, a senior consultant with the Baltimore-based Annie E. Casey Foundation, a children's advocacy group.
Pointing to signs that many children are already struggling, O'Hare added: "These raise urgent questions about whether today's children will have the resources they need to help care for America's growing elderly population."
The numbers are largely based on an analysis by the Population Reference Bureau, a nonprofit research group in Washington that studies global and U.S. trends. In some cases, the data were supplemented with additional census projections on U.S. growth from 2010-2050 as well as figures compiled by the Annie E. Casey Foundation's Kids Count project.
Nationwide, the number of children has grown by 1.9 million, or 2.6 percent, since 2000. That represents a drop-off from the previous decade, when even higher rates of immigration by Latinos _ who are more likely than some other ethnic groups to have large families _ helped increase the number of children by 8.7 million, or 13.7 percent.
Percentages aside, 23 states and the District of Columbia had declines in their numbers of children in the century's first decade, with Michigan, Rhode Island, Vermont and D.C. seeing some of the biggest drops.
On the other hand, states with some of the biggest increases _ Arizona, Florida, Georgia, Nevada, North Carolina and Texas _ also ranked in the bottom one-third of states in terms of child well-being as measured by the Kids Count project. The project calculated child well-being based on levels of poverty, single-parent families, unemployment, high-school dropouts and other factors.
The slowing population growth in the U.S. mirrors to a lesser extent the situation in other developed nations, including Russia, Japan and France which are seeing reduced growth or population losses due to declining birth rates and limited immigration. The combined population of more-developed countries other than the U.S. is projected to decline beginning in 2016, raising the prospect of prolonged budget crises as the number of working-age citizens diminish, pension costs rise and tax revenues fall.
Japan, France, Germany and Canada each have lower shares of children under age 15, ranging between 13 percent in Japan and 17 percent in Canada, while nations in Africa and the Middle East have some of the largest shares, including 50 percent in Niger and 46 percent in Afghanistan, according to figures from the United Nations Population Division.
In the U.S., the share of children under 15 is 20 percent.
Depending on future rates of immigration, the U.S. population is estimated to continue growing through at least 2050. In a hypothetical situation in which all immigration _ both legal and illegal _ immediately stopped, the U.S. could lose population beginning in 2048, according to the latest census projections.
Since 2000, the increase for children in the U.S. _ 1.9 million _ has been due to racial and ethnic minorities.
Currently, 54 percent of the nation's children are non-Hispanic white, compared to 23 percent Hispanic, 14 percent black, and 4 percent Asian.
Over the past decade, the number of non-Hispanic white children declined 10 percent to 39.7 million, while the number of minority children rose 22 percent to 34.5 million. Hispanics, as well as Asians, Native Hawaiians, Pacific Islanders and multiracial children represented all of the growth. The number of black and American Indian children declined.
In nearly one of five U.S. counties, minority children already outnumber white children.
"The `minority youth bulge' is being driven primarily by children in immigrant families," said Mark Mather, associate vice president of the Population Reference Bureau who co-wrote a report released Tuesday on the subject. "They are transforming America's schools, and in a generation they will transform the racial-ethnic composition of the U.S. work force."
"Policymakers are paying a lot of attention to the elderly, but we have a large population of children who have their own needs," he said.
The numbers come as states around the nation are seeking to cut education spending and other programs _ rather than raise taxes _ to close gaping budget holes as schools districts run out of $100 billion in federal stimulus money that helped stave off job losses over the past two years.
In Texas, for instance, the Legislature changed state law so it could slash education spending by $4 billion over the next two years to help make up for a $27 billion budget shortfall. The move is the first cut in per-student spending in Texas since World War II, even as the state has gained nearly 1 million children over the past decade, many of them Hispanic.
The school cutbacks are expected to have a disproportionate effect on low-income communities which are less able to raise local school taxes. Advocates believe that could further widen the achievement gap between students of different races in states like Texas, where some of the fastest student growth is among those who are poor and whose primary language is not English.
The resulting cuts will be far-reaching and surprising to many parents and communities, from teacher layoffs to reductions in extracurricular programs and ballooning class sizes, said Jenny LaCoste-Caputo, a spokeswoman for the Texas Association of School Administrators.
"When people say, `Cut government spending,' they don't think about the impact on the school down the street, until local voters begin to see the harm later," she said. "That's when we will really see the backlash. The sad thing is we'll have many kids suffer in the process."
Similar battles over education funding have played out in California, Pennsylvania, Ohio, Florida and Wisconsin.
Other census findings:
_Based on current trends, Florida could surpass New York as the third-largest state in overall population before the next census in 2020, part of a long-term migration of U.S. residents to the South and West. The most populous states are California and Texas.
_While more than half of U.S. residents now live in suburbs, the number of people living in cities also has rebounded somewhat in the past decade, increasing by 3 percentage points. Roughly one-third of the U.S. population lives in cities, the highest share since 1950.
Census Bureau: http://www.census.gov
Population Reference Bureau: http://www.prb.org/
Kids Count: http://www.kidscount.org