Census, U.S.

Why Do We Need a Census?

The census has grown since 1790 to cover many more questions than simply “Who lives here?” It now covers a wealth of socioeconomic data used for myriad public policies. Economic questions were added in the late 19th century; questions about unemployment date back to 1930; a housing census was introduced in 1940; and questions on commuting appeared in 1960. The most recent decennial census added questions about grandparents caring for their grandchildren and about same-sex partners. The 2000 census was used as the basis for distributing more than $280 billion annually in federal assistance to communities.

[Page 33]Although the census aims to provide a consistent historical record, questions and definitions must change to reflect changing social values and beliefs. For instance, in 1790, a decision was made to count all slaves as three fifths of a person; after the Civil War, this was no longer acceptable. In 2000, people were allowed for the first time to describe themselves as belonging to two or more race groups, rather than having to pick just one. Thus, the census also reflects the way society defines itself.

Many GIS analyses rely directly on census data. For example, census data on the time, mode, and origin and destination of work trips are used to answer questions such as the following: How many trips are being made by people driving alone compared with those carpooling or taking public transit? What are the peak travel times on different parts of the transportation network? Do wealthier people make different travel choices? Census data thus provide a basis for models that forecast downtown parking demand, the cost-effectiveness of public transit routes, and future changes in travel patterns. Innumerable other examples of the application of census data exist.

Census data also offer a useful benchmark for analyses based on more specialized data. Demographic information about neighborhood residents can help environmental analysts assess the danger that a parcel of contaminated land poses to children or frail, elderly people in a community. Spatially detailed socioeconomic information can help determine how the risks (and consequences) of major floods are distributed among community residents.

Structure of the Census

What is commonly referred to as “the census” is the “Census of Population and Housing,” just one of many major surveys conducted by the Census Bureau. The Economic Census (covering different sectors, such as manufacturing, agriculture, and distribution) is conducted every 5 years, in years ending in 2 and 7. The Economic Census, however, provides relatively little spatial detail, as it would be difficult to protect the confidentiality of businesses in many cases.

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