By The Associated Press

For the first time, racial and ethnic minorities make up more than half the children born in the U.S., capping decades of heady immigration growth that is now slowing.

New 2011 census estimates highlight sweeping changes in the nation's racial makeup and the prolonged impact of a weak economy, which is now resulting in fewer Hispanics entering the U.S.

Minorities made up roughly 2.02 million, or 50.4 percent of U.S. births in the 12-month period ending July 2011. That compares with 37 percent in 1990.

"This is an important landmark," said Roderick Harrison, a former chief of racial statistics at the Census Bureau who is now a sociologist at Howard University. "This generation is growing up much more accustomed to diversity than its elders."

The report comes as the Supreme Court prepares to rule on the legality of Arizona's strict immigration law, with many states weighing similar get-tough measures.

"We remain in a dangerous period where those appealing to anti-immigration elements are fueling a divisiveness and hostility that might take decades to overcome," Harrison said.

Hispanics make up 30 percent of Arizona's population, 70 percent of whom were born in the U.S. Hispanic births made up 42% of all births in Arizona in 2010, according to the Pew Hispanic Center. Last year, the Brookings Institution released a report revealing that white children were already in the minority in the metro areas of Phoenix, Dallas, Atlanta and Orlando.

There are also several states with large differences in ethnic and racial makeup between the elderly and the young. The largest gap among nonrural counties is Yuma County, Ariz., where 73 percent of senior citizens are white, compared with 18 percent of people under 20. Overall, Arizona has a 63 percent older white population and a 42 percent white child population.

In all, 348 of the nation's 3,143 counties, or 1 in 9, have minority populations across all age groups that total more than 50 percent. In a sign of future U.S. race and ethnic change, the number of counties reaching the tipping point increases to more than 690, or nearly 1 in 4, when looking only at the under age 5 population.

The counties in transition include Maricopa (Phoenix), Ariz.; King (Seattle), Wash.; Travis (Austin), Texas; and Palm Beach, Fla., where recent Hispanic births are driving the increased diversity among children.

Of the 30 large metropolitan areas showing the fastest Hispanic growth in the previous decade, all showed slower growth in 2011 than in the peak Hispanic growth years of 2005-2006, when the construction boom attracted new migrants to low-wage work. They include Phoenix; Atlanta; Las Vegas; Lakeland, Fla.; Charlotte, N.C and Provo, Utah.

As a whole, the nation's minority population continues to rise. Minorities increased 1.9 percent to 114.1 million, or 36.6 percent of the total U.S. population, lifted by prior waves of immigration that brought in young families and boosted the number of Hispanic women in their prime childbearing years.

The census estimates used local records of births and deaths, tax records of people moving within the U.S., and census statistics on immigrants. The figures for "white" refer to those whites who are not of Hispanic ethnicity.