After verifying millions of addresses, the U.S. Census Bureau is kicking off a campaign to recruit and hire as many as 500,000 temporary workers to help with the largest head count in U.S. history next spring, an agency official said Tuesday.

Timothy Olson, the agency's associate director for field operations, said 32,000 workers verified 50 million addresses over an almost two-month period that ended more than a week ago. Olson called the address verification process a success.

"It worked," Olson said at a news conference in Phoenix. "Until it works, you don't feel good, and I was so relieved."

The agency already has applications from 900,000 people for 2020 Census jobs, but the bureau wants a potential pool of 2.7 million applicants to choose from. Most of the hiring will be done in the first quarter of next year.

The 2020 Census head count will be the first decennial census in which respondents are encouraged to answer questions online, though they will also be able to answer questions by telephone and with mail-in paper questionnaires.

Most of the workers will be used for visits to households that don't respond. The pay for the part-time work will range from $13.50 to $30 an hour.

Census officials have acknowledged the challenges of hiring in a tight labor market and are launching paid advertisements this week to recruit applicants.

The 2020 Census will help determine how many congressional seats each state gets, as well as the allocation of hundreds of billions of dollars in federal spending.

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Separately, seven former Census Bureau directors on Tuesday wrote an open letter to congressional leaders, urging them to fully fund Census Bureau operations as soon as possible. Without that funding, they said the bureau's 2020 Census efforts could be hampered.

The letter noted that President Donald Trump's 2020 request for $5.3 billion in new funding for the census was below the House of Representatives' $7.5 billion request and the Senate Appropriations Committee's $6.7 billion.

"We believe that the Census Bureau stands the best chance of conducting a census that counts all states, localities, communities, and population groups at equal levels of accuracy and coverage, if the director and senior officials know the resources available for final preparations and the entire enumeration process as soon as possible," the letter said.

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