The Urban and Rural Classifications, Summaries of Statistics

Download The Urban and Rural Classifications and more Summaries Statistics in PDF only on Docsity! The Bureau of the Census defines urban as comprising all territory, popu- lation, and housing units located in urbanized areas and in places of 2,500 or more inhabitants outside of UAs. The term urban refers to both kinds of geographic entities. The terms urban, urbanized area, and rural are the Census Bureau’s definitions; other Federal agencies, State agencies, local officials, and private groups may use these same terms to identify areas based on different criteria. Urbanized Areas (UAs) A UA is a continuously built-up area with a population of 50,000 or more. It comprises one or more places—central place(s)—and the adjacent densely settled surrounding area—urban fringe—consisting of other places and nonplace territory. Urban Places Outside of UAs Outside of UAs, an urban place is any incorporated place or census des- ignated place (CDP) with at least 2,500 inhabitants. A CDP is a densely settled population center that has a name and community identity, and is not part of any incorporated place (see Chapter 9, “Places”). Rural Places and Territory Territory, population, and housing units that the Census Bureau does not classify as urban are classified as rural. For instance, a rural place is any incorporated place or CDP with fewer than 2,500 inhabitants that is located outside of a UA. A place is either entirely urban or entirely rural, except for those designated as an extended city. Extended Cities An extended city is an incorporated place that contains large expanses of sparsely populated territory for which the Census Bureau provides sepa- rate urban and rural population counts and land area figures. Urban and Rural Classifications 12-1 The Urban and Rural Classifications Chapter 12 Components of the Urban and Rural Classifications 12-2 Urban and Rural Classifications The Census Bureau defines UAs and extended cities for statistical purposes only; that is, for the purpose of presenting its data. Although some other geographic statistical entities, such as census tracts and CDPs, originate from agreement and cooperative action with local governmental officials and other outside groups, the development and implementation of cri- teria for defining and delineating UAs and extended cities has been largely the responsibility of the Census Bureau from the inception of the concept. This chapter discusses (1) the Census Bureau’s criteria for classifying areas as urban (with an emphasis on the definition of UAs and extended cities), (2) the procedures used to establish UAs and update their boundaries, and (3) the relationship of UAs to other geographic entities. The Census Bureau applies the same urban and rural definitions to all parts of the United States, Puerto Rico, and the Outlying Areas. Puerto Rico has both UAs and urban places outside of UAs; the Outlying Areas—American Samoa, Guam, the Northern Mariana Islands, Palau, and the Virgin Islands of the United States—have only urban places. Background Early Definitions of Urban Statistics by urban and rural categories have figured in decennial census publications for over a century.1 In the censuses of 1880, 1890, and 1900, the Census Office (predecessor of the Census Bureau) published tables based on minimum sizes of 8,000, 4,000, and 2,500 inhabitants; the latter figure was officially adopted for the 1910 census. In the decennial cen- suses from 1910 through 1940, urban comprised all territory, people, and housing units in incorporated places of 2,500 or more. In addition, some areas—usually minor civil divisions (MCDs)2—were classified as urban under special rules relating to population size and density. This definition of urban was not adequate because (1) it excluded many large, densely settled population concentrations merely because they were not part of any incorporated place, and (2) it continued to classify many large, densely built-up areas as rural in spite of the special rules that Urban and Rural Classifications 12-5 Table 12-1. (cont.) Density requirement At least 1,000 people per square mile Place population in urban fringe • Incorporated places with at least 2,500 people • CDPs if at least 5,000 people (except New England) • Some CDPs if at least 1,000 people—this lower threshold applied if an incorporated place of at least 25,000 inhabitants could join with contiguous places of any size (and a density of at least 1,000 people per square mile) to reach a total population of at least 50,000. Other features Introduction of extended cities Number of UAs A total of 275 1980 Central place requirement Incorporated place (any size) within a densely settled area of at least 50,000 population Method of boundary delineation Blocks, small EDs in certain situations Density requirement At least 1,000 people per square mile Place population in urban fringe Incorporated places of at least 2,500 people Other features • Whole-town CDPs (MCDs in New England, Michigan, New Jersey, New York, Pennsylvania, and Wisconsin having at least 95 percent of their population and at least 80 percent of their land area qualifying for inclusion in the UA were included in their entirety in the UA—applicable only to the 1980 census). • First CDPs in New England UAs Number of UAs A total of 366 1990 Central place requirement Incorporated place of any size within a densely settled area of at least 50,000 population; CDP of any size permitted as central place Method of boundary delineation Blocks exclusively Density requirement At least 1,000 people per square mile Place population in urban fringe Whole place test, minimum CDP population of generally 2,500 Other features Intercensal UAs, new titling provisions for UAs Number of UAs A total of 405 12-6 Urban and Rural Classifications national and State levels (for some individual counties and UAs the effects have been more evident). Since the 1970 census, changes in the minimum size criterion to qualify as a central place have permitted the delineation of UAs around smaller pop- ulation centers. For 1990, there was no size requirement for a central place. The inclusion of CDPs in the urban fringe, which began in 1960, and the increasing liberalization of the minimum population size requirements for CDPs, mark a continuing local involvement and interest in these geographic entities. In 1980, the Census Bureau delineated CDPs in the UAs of the six New England States (no CDPs had been delineated in New England UAs previously). For 1990, the change of the designation central city to central place further underlined the importance of CDPs in UA delineations. Changes for the 1990 Census Before each decennial census, the Census Bureau reviews the criteria for delineating UAs and extended cities. As a result of this review, the Census Bureau historically has proposed improvements to assure that these enti- ties consistently measure the Nation’s settlement pattern. The Census Bureau then publishes the proposed criteria in the Federal Register and solicits comments from the data-using public. Where necessary, further revisions are made before the final criteria are published. For 1990, the following major changes were made: • Through the 1980 census, the urbanized area delineation process had taken place only once every decade, at the time of the decennial census. Beginning in 1986, the Census Bureau allowed the delineation of new UAs on the basis of a special census taken in the intercensal period. Two areas (Davis, CA, and Merced, CA) qualified as UAs on the basis of a special census; two others (Bowling Green, KY, and Elizabethtown- Radcliffe, KY) did not. • Areas that had been UAs in a previous census were not automatically grandfathered if their 1990 population fell below 50,000. As a result, two areas that had been UAs in 1980 (Danville, IL, and Enid, OK) were no longer UAs in 1990. Urban and Rural Classifications 12-7 • 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 Table 12-1). • Extended cities had been defined in 1970 and 1980 solely for UA delin- eation purposes; for 1990, the Census Bureau broadened the concept to include extended cities outside of UAs. In addition, there were slight changes in the rules for including areas of nonresidential urban land, and more precise provisions for merging con- tiguous UAs. A major operational shift for 1990 was the introduction of an interactive delineation process and the decentralization of the UA delin- eation work, which was accomplished by the Census Bureau’s 12 regional offices, with final approval from headquarters. Criteria for UAs and Extended Cities in the 1990 Census 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.4 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, non- residential urban land use, closure of indentations or enclaves, or undevel- opable 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. Whole Place Qualification 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 12-10 Urban and Rural Classifications Enclaves are low-density areas surrounded by territory that is in the UA. Enclaves almost always consist of territory outside of any place (rarely are they incorporated places or CDPs); the surrounding territory may be in a place, or it may consist of nonplace territory. As with indentations, the inclusion of enclaves gives the UA a more regular appearance and simpli- fies data presentations. An enclave is included in the UA if it is five square miles or less in size and surrounded by territory that has an average den- sity of at least 1,000 people per square mile. Both conditions must apply. Exclaves occur where an outlying piece of a place is physically separated from the main part of the place by intervening territory that does not qualify for inclusion in the UA. The intervening territory consists of either territory outside of any place or—less frequently—in another place. Places with exclaves usually are incorporated places (most CDPs consist of one contiguous piece of territory). An exclave can never consist of territory outside of any place. Exclaves always are included in the UA when their parent place is in the UA; the criteria for density, continuous develop- ment, and road connection do not apply to exclaves. Extended Cities Some incorporated places include large expanses of vacant or very sparsely populated territory that are essentially rural in character. In general, this situation results from (1) extensive annexation of adjacent undeveloped territory, (2) governmental consolidation of an incorpo- rated place with an MCD or county, or (3) formation of a new incor- porated place from several sparsely populated MCDs. An incorporated place is considered to be an extended city if it contains one or more areas that: • Are 5 square miles or more in size. • Have a population density less than 100 people per square mile. • Comprise at least 25 percent of the total land area of the place. • Consist of 25 square miles or more. The first two conditions, and either the third or the fourth, must apply. Urban and Rural Classifications 12-11 The rural portion of an extended city may consist of several separate pieces of territory, provided that each piece is at least 5 square miles in size and has a density less than 100 people per square mile. The urban portion of an extended city consists of territory that has a density of at least 100 people per square mile. Along with jumps, nonresidential urban land use, and unde- velopable territory, extended cities are another instance where portions of the UA can have a density less than 1,000 people per square mile. The criteria for jumps, indentations, and enclaves also apply within extended cities, except that the density thresholds are lower—50 and 100 people per square mile for qualifying blocks instead of 500 and 1,000 people per square mile. If the extended city has low-density exclaves that are adjacent to its rural portions, these exclaves become part of the rural portion. There is no minimum total population for UA extended cities; however, non- UA extended cities must have at least 2,500 inhabitants. Before the 1990 cen- sus, the Census Bureau defined extended cities only for incorporated places inside UAs. The delineation of non-UA extended cities provides better pop- ulation density statistics for the Nation’s urban population by excluding those portions of incorporated places that contain vast expanses of empty or near- empty land. (Refer to Table 9-2 in Chapter 9, “Places.”) Qualification of UAs All candidate or potential UAs that have a 1990 census population of 50,000 or more qualify as UAs and appear in the 1990 census data presentations. Those potential areas that have a 1990 population below 50,000 fail to achieve urbanized status; however, their incorporated places and/or CDPs are con- sidered non-UA urban places if they have at least 2,500 inhabitants. Retention or Merger of UAs The Census Bureau never creates a new UA from the territory of an existing UA, nor does it ever transfer large portions of populated territory from one UA to another. Where two or more UAs are contiguous, the Census Bureau decides whether to maintain separate UAs or to merge them into a single 12-12 Urban and Rural Classifications UA. In many instances, the decision hinges on the location of the UAs with- in metropolitan areas (MAs). The MAs are geographic entities established by the Federal Office of Man- agement and Budget (OMB). The general concept of an MA is that of a core area containing a large population nucleus, together with adjacent commu- nities that have a high degree of economic and social integration with that core area. The fundamental geographic units of MAs are counties, except in New England, where they are cities and towns. The term MA is a collective one; individual MAs are metropolitan statisti- cal areas (MSAs), consolidated metropolitan statistical areas (CMSAs), or primary metropolitan statistical areas (PMSAs). Qualification as an MSA requires the presence of a city of at least 50,000 population, or a UA and a total population of at least 100,000 (75,000 in New England). The MSA’s geo- graphic extent is a function of commuting patterns and other specified characteristics such as population density. Within an area that qualifies as an MSA and also has a population of one million or more, individual com- ponent areas are identified if specified criteria are met and local opinion supports separate identification. These component areas are designated PMSAs, and the entire area containing the PMSAs is designated a CMSA. If no PMSAs are defined, the entire area is designated an MSA. (For further information on MAs, see Chapter 13, “Metropolitan Areas.”) Contiguous UAs maintain their separate identity when: • The UAs are entirely or mostly in different MSAs or CMSAs. • The major portion of the UA territory is in the same CMSA but in different PMSAs. • The largest central place of one UA is mostly outside of the MA that encompasses the other UA. The Census Bureau generally merges contiguous UAs when major portions of the UA territories are located in the same MSA or PMSA. In addition, all of the following conditions must be present: • There is continuous development, with no more than one jump in each Urban and Rural Classifications 12-15 Delineation of UAs and Extended Cities for the 1990 Census The 1990 UA delineation operation involved an examination of 635 poten- tial UAs, including all or parts of 1,155 counties. These included all previous UAs, those that had qualified on the basis of a special census in the 1980s, all areas that had failed to qualify in 1980, and new areas that might qualify for the first time in 1990. Because of the extensive geographic scope of the operation, and because of the lengthy, labor-intensive nature of UA deline- ation work, the Census Bureau automated much of the task by using the TIGER data base and customized UA delineation software.7 The 1980 UA boundaries were digitized and inserted into the TIGER data base, as were all representations of 1980 nonresidential urban land use, jumps, and undevelopable territory. For population concentrations that were not UAs in 1980, the Census Bureau digitized the boundaries of the central place(s) to serve as a starting point for making the 1990 UA deter- minations. Potential extended cities also were identified. To perform the UA delineations, the Census Bureau developed interactive software that featured a visual screen display of census block densities from which small-area units were created. The software could display an entire UA, sometimes involving as many as five counties, on an interactive graphics terminal. Other advantages of the UA delineation software were its ability to: • Display area and density tables. • Plot line features. • Display nonresidential urban land use. • Measure both road and straight-line distances. • Aggregrate census blocks for analysis. In addition, the software made it possible to perform numerous edits for consistency and completeness, and, ultimately, to assign the appropriate urban or rural classification code to each block in the TIGER data base. 12-16 Urban and Rural Classifications Classification as Urban or Rural For UAs that qualified in earlier censuses, the 1990 delineation process began at the previous (usually 1980) UA boundary. In the case of potential UAs, the boundary of the central place(s) was the starting point for exam- ining territory to determine qualification. Portions of surrounding territory were added to the core if they had a population density of at least 1,000 people per square mile, or if they could be included through recognition of a whole place, an extended city, a jump, a nonresidential urban land use area, or by virtue of being undevelopable territory (see previous section). For making specific delineation decisions, the Census Bureau frequently relied on small geographic entities called analysis units (AUs). Each AU consisted of either a single census block or—more frequently—a cluster of contiguous blocks, often of similar physical size and shape. An AU generally represented a single housing cluster, other territory having a closely spaced street pattern, or territory having a similar population density or land use. The Census Bureau established AUs to decide what pieces of territory to include or exclude. Staff used the automated system to measure and evaluate the following kinds of areas as AUs: core areas of places, outly- ing clusters of high-density blocks, gaps in the pattern of continuous development (usually potential jumps), urban and rural components of extended cities, indentations, and enclaves. In all these situations, the grouping of blocks into AUs established an interpretative grid of small- area geographic units. The census blocks within each AU eventually were classified as either urban or rural. Delineation Results for 1990 After the determination of UA boundaries, there followed the separa- tion or merger of contiguous UAs and the determination of UA central places and titles. Ultimately, the Census Bureau recognized 405 UAs for the 1990 census—396 in the United States and 9 in Puerto Rico. In addi- tion, the Census Bureau recognized 4,019 urban places outside of UAs— Urban and Rural Classifications 12-17 3,938 in the United States and 81 in Puerto Rico and the Outlying Areas. Of the 280 extended cities that the Census Bureau identified in the United States (none in Puerto Rico and the Outlying Areas), 128 were located inside UAs and 152 outside of UAs. Geographic Relationships and Patterns Places, Nonplace Territory, and Population Density The use of places as geographic building blocks often has an effect on the size, shape, and extent of a UA, especially where the UA consists mostly of places. Incorporated places and CDPs frequently contain low-density areas (less than 1,000 people per square mile) that would not qualify for inclusion in the UA had the territory been outside of any place. Therefore, a UA whose urban fringe consists mostly of places may include more sparsely settled territory than a UA whose fringe contains mostly nonplace territory. As a result, the urban fringe of a UA consisting mostly of places often has a lower population den- sity than a UA whose urban fringe is mostly nonplace territory. Metropolitan Areas Since 1980, UAs have been used as one of the criteria for designating an area as metropolitan. A UA also can play a role in determining the geographic extent of an MSA or CMSA. In general, a UA represents the densely settled portion of an MA, and nearly every MSA/CMSA contains at least one UA at its core. The UAs generally cover much smaller geographic areas than do MAs and have much higher average population densities. Two or more UAs may exist within a single MA. Conversely, a UA may extend into more than one MA or into nonmetropolitan area; some UAs are located entirely outside metropolitan areas. Other Geographic Entities The urban and rural classifications may be applied to many of the geo- graphic entities recognized by the Census Bureau (refer to Figure 2-1 12-20 Urban and Rural Classifications No other report series contain data on UAs, although all contain summaries for urban and rural population and housing data. However, the following individual nationwide reports, sometimes composed of multiple volumes, are devoted to UAs; each also contains the two-page UA summary map. CP-1-1C General Population Characteristics for Urbanized Areas (100-percent data) CP-2-1C Social and Economic Characteristics for Urbanized Areas (mostly sample subjects) CH-1-1C General Housing Characteristics for Urbanized Areas (100-percent data) CH-2-1C Detailed Housing Characteristics for Urbanized Areas (generally sample subjects) For the 1990 UA program, the Census Bureau produced a two-volume sup- plementary report, CPH-S-1-2, Urbanized Areas of the United States and Puerto Rico, containing UA tables and maps that appear in the separate State reports of the CPH-2 series.10 Computer Tape Files and CD-ROMs The Census Bureau’s Summary Tape Files (STFs) and other machine-read- able data products provide statistics with greater subject-matter detail than is shown in the printed reports. Each STF presents a particular set of data tables for specific types of geographic entities, with further subdivision into three or more file types (indicated by a letter suffix). The following STFs provide data for UAs and for urban and rural categories: STF 1B 100-percent data for the full geographic hierarchy to block level STF 1C 100-percent data for UAs, urban and rural (summaries by State) STF 2C 100-percent data for UAs, urban and rural (summaries by State) STF 3A Sample data for UAs, urban and rural STF 3C Sample data for UAs STF 4B Sample data for urban and rural (summaries by State) STF 4C Sample data for UAs, urban and rural (summaries by State) The STFs 1B, 1C, 3A, and 3C also are available in compact disc—read-only memory (CD-ROM) format. Urban and Rural Classifications 12-21 In machine-readable data products, each UA is identified by a four-digit numeric code and name. Where an MA and a UA have the same name, the UA code and the MA code are identical. If MA title cities represent multi- ple UAs, or the UA title city does not correspond to the first name of an MA title, the Census Bureau has assigned a code based on the alphabetical sequence of the UA title in relationship to the other UA and MA titles. Treatment of the Rural Category In the 100-percent data products, the rural classification is subdivided into two categories: places of less than 2,500 outside UAs (rural places), and not in places. The not in places category comprises (1) rural territory, pop- ulation, and housing units outside incorporated places and CDPs, and (2) the rural portions of extended cities.11 In many data products, the term other rural is used; other rural is a residual category specific to the classification of the rural population and housing units in each data product. In the sample data products, rural population and housing units are sub- divided into rural farm and rural nonfarm. Rural farm comprises all rural households and housing units on farms (places from which $1,000 or more of agricultural products were sold in 1989); rural nonfarm com- prises the remaining rural population and housing units. Other Map Products and Computer Files The Census Bureau has produced individual Urbanized Area Boundary Maps. These maps are electrostatically plotted and portray the UA bound- ary and the names of all UA boundary features, along with the boundaries of States, counties, county subdivisions (MCDs and CCDs), AIANAs, places, and selected base map features such as major interstate and Federally main- tained highways and water bodies. The format usually features a single UA on a standard paper map sheet (not to exceed 36 inches by 42 inches). The Census Bureau also offers a machine-readable TIGER UA Limit™ file on magnetic tape. This national file contains a digital representation of the geographic coordinates for all linear features in the TIGER data base 12-22 Urban and Rural Classifications that comprise the 1990 UA boundaries. In addition, the TIGER/Line™ files, 1992, contain the 1990 UA codes and identify every feature that comprises the boundary of each UA along with all the normal TIGER attributes for each feature.