Our country is taking attendance to see who's here. A national Census -- required by the Constitution -- takes place every 10 years to determine how many U.S. House members each state has, based on population. Results are used to draw congressional and state legislative districts. They also affect how more than $675 billion in federal money is split among communities for public safety, health care, schools, job training, roads, bridges, other public works and more. This is the 24th time that the United States has counted its population since 1790.

Postcards now going to each household ask Americans to respond to a 2020 census questionnaire online or by mail, starting this week. (The official count date is April 1 – "Census Day.") The 10-minute form asks about race, age and education, but not about citizenship, income, religion or politics. Beginning in May, thousands of temporary Census Bureau workers will start ringing doorbells at houses, apartments, mobile homes and elsewhere in an effort to reach those who didn't respond – including the homeless. The count also includes noncitizens and prisoners. Although the government doesn't enforce penalties, federal law requires U.S. residents 18 and older to answer census questions – with one adult allowed to respond on a family's behalf.

This year's count is the first being taken mainly online, where the questionnaire goes live Thursday (March 12) at my2020census.gov and will be available through July 31. For those without Internet access or who prefer to stay offline, the bureau also will collect responses by phone and on paper forms, which are scheduled to arrive at some homes any time now and by early April to every household that hasn't responded yet. The web form and call centers are available in 13 languages. "We are extremely committed to reaching those people who are historically undercounted," says Director Steven Dillingham.

In print, broadcast and online ads, as well as on billboards, the government stresses the importance of an accurate tally and the secrecy of replies – which aren't shared with law enforcers or immigration officials. The Census Bureau uses encryption and other security technology to protect privacy. The $500-million ad campaign uses this slogan "Shape your Future. Start here."

Director says: "We are using the best technologies and practices to protect data confidentiality and reduce cybersecurity risks. . . . Confidentiality is a core part of the Census Bureau's culture." – Steven Dillingham

Indian chief says: "If we aren't all counted, we leave money on the table. For every one Cherokee Nation citizen who doesn't get counted, it's a loss of about $50,000 in federal funding for tribal services over the course of a decade." -- Chuck Hoskin, Cherokee Nation principal chief, Oklahoma City

When results come: The Census Bureau has until the end of December to start releasing 2020 results, beginning with state population counts. That determines how the 435 U.S. House seats are allocated after each state gets at least one.