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 *The whole place test improved the rules for inclusion of incorporated places and CDPs in the urban fringe. In addition, the Census Bureau introduced a standard minimum population threshold for CDPs in the urban fringe—2,500 inhabitants in most instances (see ). In addition, there were slight changes in the rules for including areas of nonresidential urban land, and more precise provisions for merging contiguous UAs. A major operational shift for 1990 was the introduction of an interactive delineation process and the decentralization of the UA delineation work, which was accomplished by the Census Bureau’s 12 regional offices, with final approval from headquarters.
 * Extended cities had been defined in 1970 and 1980 solely for UA delineation purposes; for 1990, the Census Bureau broadened the concept to include extended cities outside of UAs.

A UA must exhibit a pattern of continuous development out from a central core or the boundary of a UA delineated for the previous census. Existing UAs generally retain all territory that was within their previous boundaries. Areas added to the urban fringe must be contiguous to this core and must have a population density of at least 1,000 people per square mile. Areas with lower densities are permitted if they meet the criteria for jumps, nonresidential urban land use, closure of indentations or enclaves, or undevelopable territory. All area added to the UA must be connected directly by road to the main body of the UA, and this road connection must either be located within the area being added, or touch it on one side. The UA must contain at least 50,000 people.

Places are important geographic components of UAs. Except for extended cities, all incorporated places and CDPs either are included in a UA in their entirety, or excluded from it completely. A place is included in the UA if it has a qualifying core. This qualifying core is an area with a population density of at least 1,000 people per square mile that contains at least 50 percent of Notes and References Urban and Rural Classifications12-7