The many different kinds of geographic areas used by the Census Bureau to report statistical data serve various purposes, as defined by the specific use to be made of the data from a particular census, sample survey, or other program. The decennial census of population and housing provides data for the largest selection of geographic entities, including entities that are both large and small in area and those that are densely or sparsely populated. The decennial census can embrace this variety of entities because the very large number of people and housing units involved are distributed in sizable numbers throughout the Nation and its territories. The information collected in the other censuses and sample surveys conducted by the Census Bureau, such as statistics about manufacturing establishments, farms, or people unemployed, usually are more appropriate for presentation only when summarized into larger geographic entities, counties, metropolitan areas, or States. Such entities are appropriate because of the relatively small number of establishments located in many smaller areas or the small number of people involved in most sample surveys.
Despite the numerous levels of standard geography for which the Census Bureau tabulates statistical data, the existing geographic entities used to report the results of a specific census or sample survey sometimes do not match the needs of a specific user. As an example, the Census Bureau does not currently tabulate data for local school-attendance areas as part of its regular decennial census data series, yet many school boards need this level of geographic detail to help them determine the demographic characteristics of their service areas as well as to plan for school closings, new schools, and attendance-area boundary revisions. Census blocks, BGs, and census tracts or BNAs, together with county subdivisions and/or places, are typically small enough to serve as basic spatial units for aggregation into other types of analysis areas. For example, a school board generally can accumulate the statistics it needs for attendance areas by combining the data for a set of census blocks, BGs, and/or census tracts/BNAs. Increasingly, the State Data Centers, a relatively recent addition to the Census Bureau’s outreach and data dissemination program, and private companies provide these types of user-specified geographic reaggregation services in order to supply needed data tabulations.
