For the first time, the U.S. Census Bureau is distributing bilingual questionnaires to 13.5 million households in predominantly Spanish-speaking neighborhoods for its 2010 population survey.

Automatic mailing of the forms, in English and Spanish, debuts next year. In addition to Spanish, census forms will be made available in Chinese, Korean, Vietnamese and Russian upon request. That's similar to the 2000 census, when participants could request questionnaires in several languages.

But none of those other languages compares to the proliferation of Spanish. Roughly 34 million people reported speaking Spanish at home in the United States in 2007, more than all the other languages combined except English. Eighty percent of the U.S. population reported speaking only English at home.

The census is done every 10 years.

Latino advocates hope the forms will lead to a more accurate count by winning over the trust of immigrants who are often wary of government and may be even more fearful after the recent surge in immigration raids and deportations.

"If the government is reaching out to you in a language you understand, it helps build trust," said Arturo Vargas, executive director of the National Association of Latino Elected and Appointed Officials.

Traditionally, experts say, the Census Bureau has undercounted minority and immigrant communities, who are harder to reach because of language barriers and distrust of government.

Census officials say they designed the bilingual forms after extensive research, using the Canadian census questionnaire as an example. Over a six-year testing period, officials said the forms drew a better response in Spanish-speaking areas.

The bilingual forms will be mailed out to neighborhoods where at least a fifth of households report speaking primarily Spanish and little English, said Adrienne Oneto, assistant division chief for content and outreach at the Census Bureau in Washington. More than a quarter of the forms will be distributed in California. The Miami and Houston areas will also receive sizable numbers of the questionnaires.