Undertaken by the U.S. Census Bureau every ten years ending in zero. It provides a count of the population and housing units for the entire United States. Its primary purpose is to provide the population counties that determine how seats in the U.S. House of Representatives are apportioned between the states.

A housing unit that does not provide safe and adequate shelter and in its present condition endangers the health, safety, or well-being of the occupants. HUD and the Census Bureau quantify this as a building having one or more critical defects or a number of intermediate defects that would require substantial construction to repair.

A physical or mental impairment that substantially limits one or more of the major life activities of an individual. Disabled persons qualify for Section 8 and public housing waiting list preferences. HUD's Section 811 Supportive Housing for Persons with Disabilities program provides accessible and affordable apartments for low-income persons with disabilities.

A practice has a discriminatory effect when it actually or predictably results in a disparate impact on a group of persons. A discriminatory effect also occurs when a practice creates, increases, reinforces, or perpetuates segregated housing patterns because of race, color, religion, sex, handicap, familial status, or national origin.