Census Geography

Geography is a basic element of the Census Bureau's system for organizing and presenting statistical data to the public.

There are numerous geographic entities for which the Census Bureau tabulates data. The Census Bureau uses two widely known entities, States and counties, in almost all its censuses, sample surveys, and other programs. Other geographic entities, however, appear in machine readable data summaries.

This material is excerpted from the Geographic Reference Manual issued November 1994, U.S. Dept. of Commerce, Economics and Statistics Administration, Bureau of Census.

Acknowledgements

  The Geographic Areas Reference Manual (GARM) was produced by the Geography Division, Robert A. LaMacchia, acting Division Chief and Assistant Division Chief for Planning, under the direction of Robert W. Marx, former Division Chief, and Joel Sobel, Chief, Geographic Areas Branch.

Nancy K. Torrieri directed all activities leading to the writing, review, and publication of the GARM. James B. Davis was responsible for research, presentation, and editorial review of the text. Elaine N. Gregory coordinated publication activities and review of the maps and graphics. Geography Division staff contributing significantly to the writing of the chapters were David R. Aultman, Lee C. Bush, James B. Davis, Joan F. Greendeer-Lee, Donald I. Hirschfeld, Catherine M. McCully, Joseph L. Marinucci, Catherine L. Miller, Joel C. Miller, Janemary G. Rosenson, and Beatrice L. Warren. Robert W. Marx, Joel Sobel, Nancy K. Torrieri, and Michael R. Ratcliffe of the Geography Division, and Robert C. Speaker, James D. Fitzsimmons, Richard L. Forstall, Donald E. Starsinic, and Donald C. Dahmann of the Population Division, contributed significantly to the editorial review. Charlene K. Bickings of the Geography Division designed the graphics, cover illustration, and publication layout style. Timothy F. Trainor, Connie Beard, Carl C. Sanders, April M. Robbins, and Richard E. Hartgenof the Geography Dibision oversaw the production of the maps. Wendell McManus of the Geography Division, and Martha E. Gurtz, Jacqueline R. Appell, and Carol Hendrich of the Data Preparation Division provided cartographic support. Erskie D. Greggs and Karen L. Abercrumbie of the Geography Division provided publication support. Linda H. Ambill and other staff of the Administration and Publication Services Division, Walter C. Odom, Chief, provided procurement, editorial, design, publication, and printing services.

Census TIGER****, TIGER***, TIGER/Line****, and TIGER/GICS**** are registered trademarks of the U.S. Census Bureau.

The Census Bureau's Most Commonly Used Statistical Entities

Region and Division	Combination of States
Metropolitan Area (MA)*	One or more contiguous counties (cities and towns in New England that are socially and economically integrated with a large densely settled population core
Urbanized Area (UA)	A continuously built-up area with a population of 50,000 or more
Census County Division (CCD)	A subdivision of a county that serves as the statistical equivalent of an MCD in 21 states where MCDs either do not exist or are not appropriate for decennial census data reporting purposes
Unorganized Territory (UT)	A subdivision of a county that is the statistical equivalent of an MCD for decennial census data reporting purposes in those MCD States that have counties with part or all of their area not in any MCD.
Census Designated Place (CDP)	A densely settled population concentration which has a name and community identity but is not part of any incorporated place.
Census Tract	A statistical subdivision of selected counties-established by a local commitee of data users-that is a relatively stable basis for tabulating decennial census data. Secondarily, it serves as a framework for assigning census block numbers. Tabulated parts occur where a county subdivision or place boundary divides a census tract.
Block Numbering Area (BNA)	A statistical subdivision of counties without census tracts, serving as a framework fo assigning census block numbers and for tabulating decennial census data. Tabulated parts occur where a county subdivision or place boundary divides a BNA.
Block Group (BG)	A grouping of census blocks having the same first digit in their identifying number within a census tract or BNA. Tabulated parts occur where a county subdivision or place boundary divides a BG
Census Block	The smallest Census Bureau geographic entity, it generally is an area bounded by streets, streams, and the boundaries of legal and statistical entities.

*The Census Bureau tabulates data for regions, divisions, and MAs in its data presentations for almost all censuses and sample surveys. It tabulates data for other kinds of statistical entities only in its data presentations for the decennial census of population.

The Economic Census includes the Censuses of Retail Trade, Wholesale Trade, Manufactures, Service Industries, Construction Industries, Mineral Industries, and Transportation, along with the Enterprise Statistics Program and the Minority and Women Owned Businesses Program.

The Census of Governments reports data for school districts and other special purpose districts in addition to the geographic entities in the diagram below (except for ZIP Codes). These may exist at various levels of the hierarchy. The Census of Governments includes as places only incorporated places.

Unlike the Economic and Governments Censuses, the Agriculture Census does not provide data for places or MCDs. It does report data for special purpose entities that may exist at various levels of the hierarchy.

In tabulating data, the Census Bureau is concerned with the individual's right to confidentiality. Specifically, Federal law (Title 13, U.S. Code) states that:

• The information gathered by the Census Bureau is solely for statistical purposes.
• The publication of the data must be such that neither individual establishments nor people nor their residences can be identified.
• Only sworn officers and employees of the Census Bureau may examine individual responses.

All geographic statistical entities must be defined and delineated to comply with the legal requirements and the policies specified by the Census Bureau to protect the confidentiality of the collected information. These concerns are not restricted to the geographic classification component of a census or sample survey.

To provide a national structure that supports the first requirement, the Census Bureau devises geographic entities in order to supplement, but not to replace, governmental units. To meet the second requirement, the Census Bureau structures the criteria for the various statistical entities to ensure appropriate population size thresholds. These size criteria generally permit the Census Bureau to provide meaningful demographic and economic data, and at the same time ensure confidentiality through sufficient numbers of responses within a particular geographic entity. In this way, the geographic area criteria support both the Census Bureau's confidentiality mandate and the statistical validity goal by limiting the minimum population size of most subcounty statistical entities.