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2010 census blockgroups within Fairfax County. This data was acquired from the US Census Bureau.

The 2010 census tracts within Fairfax County. This data was acquired from the US Census Bureau.

30-year population forecasts at a parcel level within Fairfax County developed on the VALID_TO date in the attribute table. For methodology and a data dictionary please view the IPLS data dictionary

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30-year housing unit forecasts at a parcel level within Fairfax County developed on the VALID_TO date in the attribute table. For methodology and a data dictionary please view the IPLS data dictionary

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The United States Census Bureau defines Blocks as a "statistical areas bounded by visible features, such as streets, roads, streams, and railroad tracks, and by nonvisible boundaries, such as selected property lines and city, township, school district, and county limits and short line-of-sight extensions of streets and roads. Generally, census blocks are small in area; for example, a block in a city bounded on all sides by streets. Census blocks in suburban and rural areas may be large, irregular, and bounded by a variety of features, such as roads, streams, and transmission lines. Census blocks nest within all other tabulated census geographic entities and are the basis for all tabulated data."

The United States Census Bureau defines a Block Group as a "statistical divisions of census tracts, are generally defined to contain between 600 and 3,000 people, and are used to present data and control block numbering. A block group consists of clusters of blocks within the same census tract that have the same first digit of their four-digit census block number. For example, blocks 3001, 3002, 3003, . . ., 3999 in census tract 1210.02 belong to BG 3 in that census tract. Most BGs were delineated by local participants in the Census Bureau's Participant Statistical Areas Program. The Census Bureau delineated BGs only where a local or tribal government declined to participate, and a regional organization or State Data Center was not available to participate.,A BG usually covers a contiguous area. Each census tract contains at least one BG, and BGs are uniquely numbered within the census tract. Within the standard census geographic hierarchy, BGs never cross state, county, or census tract boundaries but may cross the boundaries of any other geographic entity.",