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Census Block Groups Geographic Area Descriptions | Metadata
Geographic Area Description Census Block Group A census block group (BG) is a cluster of census blocks having the same first digit of their four-digit identifying numbers within a census tract. (See also Census Tract.) For example, block group 3 (BG 3) within a census tract includes all blocks numbered from 3000 to 3999. BGs generally contain between 600 and 3,000 people, with an optimum size of 1,500 people. Most BGs were delineated by local participants as part of the U.S. Census Bureau's Participant Statistical Areas Program. The U.S. Census Bureau delineated BGs only where a local, state, or tribal government declined to participate or where the U.S. Census Bureau could not identify a potential local or tribal participant. BGs never cross the boundaries of states, counties, or statistically equivalent entities, except for a BG delineated by American Indian tribal authorities, and then only when tabulated within the American Indian hierarchy. (See also Tribal Block Group.) BGs never cross the boundaries of census tracts, but may cross the boundary of any other geographic entity required as a census block boundary. In decennial census data tabulations, a BG may be split for statistical purposes for every unique combination of American Indian area, Alaska Native area, Hawaiian home land, congressional district, county subdivision, place, voting district, or other tabulation entity. For example, if BG 3 is partly in a city and partly outside the city, there are separate tabulated records for each portion of BG 3. BGs are used in tabulating data nationwide, as was done for the 1990 census, for all block-numbered areas in the 1980 census, and for selected areas in the 1970 census. For statistical purposes, BGs are a substitute for the enumeration districts (EDs) used for reporting data in many parts of the United States for the 1970 and 1980 censuses and in all areas before 1970. Return to Top | Geographic Area Descriptions | Metadata Tribal Block Group A tribal block group (BG) is a cluster of census blocks having the same first digit of their four-digit identifying numbers and are within a single tribal census tract. For example, tribal BG 3 consists of all blocks within tribal tract 9406 numbered from 3000 to 3999. Where a federally recognized American Indian reservation and/or off-reservation trust land crosses county and/or state lines, the same tribal BG may be assigned on both sides of the state/county boundary within a tribal census tract that is numbered from 9400 to 9499. The optimum size for a tribal BG is 1,000 people; it must contain a minimum of 300 people. (See also Block Group.) The difference between a tribal BG and a nontribal BG is in the hierarchical presentation of the data. A tribal BG is part of the American Indian hierarchy; that is, the tribal BG is within a tribal census tract that is within a federally recognized American Indian reservation and/or off-reservation trust land. Return to Top | Geographic
Area Descriptions | Metadata Metadata
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