The number is nearly double the 276,000 residents who reported a lack of English proficiency in the 1990 census.

The increase tracks almost exactly the growth of the Hispanic population during the decade, although speakers of languages other than Spanish are included in the total.

Spanish is by far the predominant foreign language spoken at home.

Experts point out that a lack of English proficiency has broad implications for the state's economy because higher-paying jobs require greater communication skills.

Public schools also are having to deal with a burgeoning number of schoolchildren who need extra help with language skills.

Measurement of language proficiency was one of the highlights of the survey released Tuesday, tested last year as a replacement for the "long form" questionnaire by 2010.

Estimates for the state were based on responses from more than 15,000 households. Their accuracy of the estimates will be measured against long-form data to be released in mid-2002.

Other topics of Arizona interest:

Foreign focus

More than one in seven residents of Arizona households was born in a foreign country, compared with one in nine nationwide. About three-fourths of the Arizona group are not citizens.

The census does not distinguish between legal and illegal immigrants.

More than half of the state's immigrants, or 344,000 people, came to the state since 1990.

In Maricopa County the decade's 258,000 immigrants outnumber previous entrants by 5-4.

About 1.2 million Arizona residents age 5 or older speak a language other than English at home, although not necessarily exclusively.

That represents just over one in four people in that age group, an increase from one in five a decade ago.

Spanish is spoken at home by 928,000 people. Of that group, 56 percent rate themselves as also proficient in English.

Commuting

Arizona's commuters are much more fond of carpooling than riding public transportation to work.

Still, the nearly three-fourths of state residents 16 and older who drive alone to work is slightly lower than the national average.

Although 14.9 percent of Arizona workers shared a ride to their jobs, only 2.2 percent rode public transportation, less than half the U.S. average.

The state ranked second nationally in carpooling, behind Hawaii's 17.7 percent.

Success in carpooling likely stems from the Valley's trip-reduction program, in which employers of 50 or more people are required to promote measures to reduce traffic and pollution, said Randi Alcott, ride-share manager for the Regional Public Transportation Authority.

Recent improvements in bus systems in Tempe, Phoenix, Mesa, and changes soon to come in Glendale, should boost use of public transportation, Alcott said.

The census survey did not provide an estimate of total passenger cars and trucks, but said about 300,000 households had three or more vehicles available. That's twice as many households as had no vehicle at all.

On the move

More than one in five Arizonans, or 1 million people, moved to their residence within the previous year. Nationally, the figure is 16 percent.

About one-fourth of the movers came from other states, and 1.1 percent said they came from abroad.

More than half of Arizona householders have changed residences since 1995.

The high rate of housing changes, reflecting both an influx of newcomers and shifts among people who are already residents, represents another challenge to community stability and stable school enrollment.