INDIANAPOLIS -- The director of the U.S. Census is defending the agency's spending of millions in taxpayer dollars on advertising and advance letters meant to raise awareness about this week's official mailings.

Director Robert Groves told 6News' Kara Kenney that $133 million spent on advertising and $85 million for the letters is critical to boosting response numbers.

"I'm convinced it's a very prudent use of taxpayer money because by spending $133 million on advertising, we will save hundreds of millions on staff costs to interview people face to face," he said.

Groves said that for every household, it costs 42 cents to mail and then process a completed booklet. But hiring an employee, training them and dispatching them to collect the information later costs $57 per household, he said.

"We've been tracking the census. We're at a 10-year low. Only 10 percent of the people know the census is done this month," Groves said.

That's one of the reasons he said the agency decided to take the unusual route of buying ad time during the Super Bowl and sponsoring a NASCAR driver.

"It may be unconventional, but it's an audience that's very important," Groves said. "(NASCAR) has a fan base that's disproportionately male. We find males tend not to respond more than females."

Census officials said the agency will save $85 million for every 1 percent increase in the mail-back response.

The census cost $2.5 billion in 1990 and $4.5 billion in 2000. It's expected to cost $14.7 billion this year, or about $48 a person.

Most Hoosiers will receive booklets this week. They are due by April 1.