Arizona's Hispanic population grew far faster than other groups over the past decade, and children of Hispanic ancestry now outnumber those who are white, according to the official 2010 Census numbers.

Of Arizona's population under 18 years old, 43.2 percent were Hispanic and 41.6 percent were white, the data showed.

Overall in Pima County, the Hispanic population of 338,802 makes up 34.5 percent of the population. In Tucson, there are 216,308 Hispanics, which makes up 41.6 percent of the city's population.

"That probably will surprise a lot of people outside of Arizona because Arizona is still thought of as being a pretty white state, but it isn't, especially for the younger part of the population," said William Frey, a demographer with the Brookings Institution, a nonprofit public policy organization in Washington, D.C.

Of Arizona's 6.39 million residents, 1.9 million, or 29.7 percent, were Hispanic, the data showed. The Hispanic population grew by about 600,000, or 46.3 percent, during the decade, while growth for all other groups was 17.3 percent.

Hispanics made up 25.3 percent of Arizona's population in 2000 and 18.8 percent in 1990.

The change in demographics means Arizona will have to adapt to new challenges, Frey said. For example, its education system may have to focus more on English language instruction in order to adequately prepare students, he said.

"The special needs of the diverse population does need to be taken into account, and it's especially important in times of fiscal stress, when there's a lot of resources that are being cut back for all kinds of things," Frey said.

Despite the growth shown in the census numbers, the Hispanic population fell short of the Brookings Institution's projections by more than 100,000 people, Frey said, adding that the down economy is the most likely culprit.

Jennifer Steen, a political science professor at Arizona State University, said the shortfall also could have to do with the difficulty of counting undocumented immigrants or even an exodus of immigrants in response to SB 1070.

"It's always hard to count those people in any context because they have a lot of reasons to be wary of identifying themselves to a representative of the United States government," she said.