PHOENIX — More than 990,000 people living in Arizona last year were born in other countries.

And 70 percent of them are not U.S. citizens.

The new figures today from the U.S. Census Bureau illustrate an explosion in the share of Arizona residents who came here from other countries.

That 991,584 estimate from the federal agency amounts to 15.6 percent of the state's population.

By comparison, only 12.8 percent of Arizonans were foreign-born when the official census was done in 2000. Ten years before that, the figure was 7.6 percent of the population.

While the Census Bureau pegs the number of foreign-born residents who are not U.S. citizens at slightly less than 700,000, it does not estimate how many in that group are here illegally.

But a separate report released by the U.S. Department of Homeland Security estimated Arizona's "unauthorized" population in January 2007 at 530,000, which would be about three out of every four non-citizen residents.

Homeland Security estimated a 60 percent jump from the 330,000 illegal immigrants the agency figured were in the state at the beginning of the decade.

The two reports help paint a picture of Arizona and how the population here compares with the rest of the country.

For example, the national percentage of foreign-born residents is 12.6 percent, up from 11.1 percent in 2000 and 7.9 percent in 1990.

But Arizona is not even in the top five of states in this category.

California leads with more than 27 percent of its more than 36.5 million residents having been born outside the U.S. And New York, New Jersey, Nevada, Florida, Hawaii and Texas all have higher percentages of foreign-born residents than Arizona.

At the bottom of the list is West Virginia, where just 1.3 percent of its population is foreign-born.

The Census Bureau looked at only some of Arizona's counties and cities. But the figures show the number of foreign-born residents is not dispersed equally throughout the state.

Of 10 Arizona counties studied by the Census Bureau, the figures differ somewhat.

More than 13 percent of Pima County residents are foreign-born, with nearly 61 percent of those not U.S. citizens. Homeland Security did not break down its estimates of illegal immigrants by county.

Cochise County, despite its border location, had fewer than 13 percent of its residents who said they were non-U.S.-born, about 58 percent not U.S. citizens.

But just about one out of four Yuma County residents were not born in this country.

In Maricopa County, the foreign-born population is nearly 18 percent of the total, with more than 73 percent not citizens.

Within the state's most populous county, the Census Bureau reports that Phoenix had the largest percentage of foreign-born residents, followed by Tempe, Mesa and Chandler.

The Census Bureau numbers also show a majority of those born elsewhere have been in Arizona awhile. Only about a third of those born elsewhere came here since the beginning of the decade.

Given its proximity, it's no surprise that more than seven out of 10 of those born elsewhere came from Latin America. But almost one out of eight foreign-born Arizonans are from Asia, with one out of 10 from Europe.

The report also confirms what is seen as common knowledge in many corners — that overall, a majority of Arizonans are immigrants, having come here, from another state, as well as from foreign lands.

The Census Bureau reports just 42 percent of state residents were born in Arizona, among the lowest rate in the country. The national average is more than 67 percent, with more than 82 percent of Louisiana residents being natives.

At the other extreme is Nevada, where fewer than 29 percent of current residents were born.

The report also shows that more than 28 percent of Arizonans age 5 and older speak a language other than English at home, compared with less than 20 percent nationwide. The most prevalent language for those Arizonans is Spanish, spoken in 22 percent of households.

More than 12 percent of Arizonans said they speak English "less than well." That compares with the national average of 8.7 percent. California tops the list at 20 percent.

In 2000, the Census Bureau reported that 26 percent of Arizonans spoke a language other than English at home.