(CNN) -- The army of U.S. Census Bureau personnel poised to fan out across the country will find out Wednesday approximately how many doors they're going to be knocking on to complete this year's nationwide survey.
Census Director Robert Groves is scheduled to announce at 1 p.m. ET how well Americans responded by mail to the once-a-decade census, and thereby how many homes need to be contacted directly by census workers in an effort than begins in May.
The U.S. Census Bureau announced that as of Tuesday night, 72 percent of U.S. households that were sent the census survey had mailed back, matching the rate achieved during the last census in 2000, and with some late-mail arrivals expected in coming days.
Midwestern states have turned in the highest participation rates, according to the bureau, with Wisconsin leading the country with an 80 percent rate. Minnesota follows with a 79 percent rate, then Iowa and Indiana with 77 percent and Nebraska at 76 percent.
The U.S. Census Bureau has chalked up vast array of numbers regarding the 2010 census and its importance: more than $400 billion in federal funds allocated based in part on the census, 134 million "housing units" contacted, 13.5 million bilingual (English/Spanish) questionnaires delivered in selected neighborhoods, and so on.
But there is one that cuts to the bottom line of census business:
It costs the government 42 cents for each response that comes back via mailed census form, while it costs the government an estimated $57 per household to obtain responses in person.
The latter figure can vary, according to the number of times census workers have to come knocking to get a response, the bureau says.
Taken on a grander scale, taxpayers would save $1.5 billion if everyone completed and mailed back the census questionnaire instead of requiring the hiring, training and dispatching of that army of census workers, the bureau says.
One bright economic light in all the census statistics, especially in these economically stressful times: the bureau is hiring an estimated 870,000 temporary workers as part of the 1.2 million field positions needed to conduct census operations this year.
That's more than the population of Alaska, North Dakota, Vermont or Wyoming.
Job information is available at the census Web site.