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 generally accepted criteria and guidelines for the identification and delineation of the new entity. The Census Bureau also must determine that the resulting geographic areas are suitable for tabulating and disseminating the statistical data it collects. Then it must identify sources to select and delineate the entities, usually local census statistical areas committees, State agencies, and tribal officials. The guidelines and rules for each type of area originate from (1) the requirements, needs, and preferences of the data user community; (2) the Census Bureau’s own practices in data collection, processing, and map presentation; (3) the basic methodological principles for delineating geographic areas; and (4) various other criteria for identifying statistical areas. Ultimately, cost and the policies of the Federal Government form a critical underlying consideration with which the Census Bureau must deal in selecting the geographic entities for which it will provide data from its censuses and sample surveys. These elements provide a framework that defines what can be done. Within that framework, data user needs and statistical practice influence the conceptual approaches used by the Census Bureau.

National consistency is an important consideration for the Census Bureau’s geographic classifications and presentations. It is important for legal/administrative entities, particularly those comprising the basic State/county/MCD/place hierarchy. Consistency is especially relevant to statistical areas, where the Census Bureau is largely responsible for establishing and implementing the criteria, standards, and guidelines that define these areas. Using a uniform approach to control the identification and delineation of, and data presentations for, those geographic areas that are numerous and widespread (such as census blocks, BGs, census tracts and BNAs, CCDs, CDPs, UAs, and MAs) ensures a national consistency.

One of the great virtues of decennial censuses is that they provide statistics spanning nearly two centuries, thereby making possible many time-series studies. Over the last several decades, the content of the decennial census questionnaire and the methodology used to tabulate and disseminate the 2-26Geographic Overview