general problem of why the seemingly simple topic of residence can be so dauntingly complex to both census designers and respondents (Sections 2–C and 2–D). We outline some of the consequences of difficulties in defining residence in Section 2–E, and close in Section 2–F with a description of the Census Bureau’s preliminary residence rules for 2010.


The explicit constitutional mandate for the decennial census is the generation of counts used to apportion the U.S. House of Representatives. Through this action—assignment of the number of seats in the House and, accordingly, the number of votes in the electoral college for president—representative power is distributed among the states. Hence, the accurate placement of residents by their geographic location (at least to the state level) has always been key to the accuracy of the census.

A related use of census data—and arguably as primary a use as apportionment—is the division of states into legislative and voting districts. The use of the census for redistricting greatly heightens the need for accurate links between people and geographic locations: the redrawing of districts demands data at the fine-grained resolution of blocks and tracts. According to McMillen (2000b), in the early days of the country, the division of states into legislative areas (redistricting) was left primarily to the states. In 1842, Congress enacted a law requiring states with more than one legislative district to divide the state into districts with one representative per district. However, nothing was said about district size until the latter half of the 1800s, when geographical compactness and equal population emerged as requirements. In 1929, Congress passed a permanent apportionment act that contained no directives on the geographic size or population of districts, beginning a period of great variability in legislative districts. This period lasted until the U.S. Supreme Court’s ruling in 1962 (Baker v. Carr, 369 U.S. 186) that required legislative districts within states to be drawn to include equal numbers of people (McMillen, 2000b). In the wake of that ruling, and other cases that reinforced the “one person, one vote” standard, legislative redistricting is now based entirely on the most recent decennial census counts, and districts are held to exacting standards of numerical equivalence in population. Since 1965, enforcement of the Voting Rights Act and protection of minority rights have also depended on census counts.

Another important use of census counts is in the distribution of funds by the federal government to the states and substate units. In 1998, $185 billion in federal aid was distributed to states and substate areas based in whole or part on census counts (U.S. General Accounting Office, 1999).

In all of these uses of census data, the need to count each person once,

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