To classify people as poor, the Census Bureau uses a set of money income thresholds that vary by family size and composition. If a family's total income is below the poverty threshold relevant to that family, then every individual in the family is classified as poor. The official poverty thresholds do not vary geographically, but they are updated for inflation using the Consumer Price Index (CPI-U). The official poverty definition uses money income before taxes as its measure of income, and does not include capital gains or the monetary value of noncash benefits such as public housing, Medicaid, and food stamps. For more information, see the Census Bureau’s poverty definitions.

The Current Population Survey defines a family as a group of two people or more (one of whom is the householder) related by birth, marriage, or adoption and residing together; all such people (including related subfamily members) are considered as members of one family. Beginning with the 1980 Current Population Survey, unrelated subfamilies (referred to in the past as secondary families) are no longer included in the count of families, nor are the members of unrelated subfamilies included in the count of family members.

In 2002, there were substantial changes in the racial categories used by the Census Bureau. Time series by race that include data from both racial classifications should be interpreted with care. More details on the changes in racial categories.