Thursday is the deadline to fill out and return 2010 census forms.
The responses to the 10 questions help determine how more than $400 billion in federal money is allotted to local, tribal and state governments every year, including money for roads, health care, schools and other critical programs.
The census is also used to redraw state and local legislative boundaries.
Participating in the once-a-decade count is required by law for everyone living in the United States.
The Census Bureau projects that it will have to send census takers to an estimated 48 million households that do not respond by mail.