Census tract

A census tract, census area, census district or meshblock[1] is a geographic region defined for the purpose of taking a census.[2] Sometimes these coincide with the limits of cities, towns or other administrative areas[2] and several tracts commonly exist within a county. In unincorporated areas of the United States these are often arbitrary, except for coinciding with political lines.

Census tracts represent the smallest territorial entity for which population data are available in many countries.[3] In the United States, census tracts are subdivided into block groups and census blocks. In Canada they are divided into dissemination areas. In the U.S., census tracts are "designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions" and "average about 4,000 inhabitants".[4]

By country

Brazil

The Brazilian Institute of Geography and Statistics uses the term census sector (setor censitário)[5]. As of the 2010 Census, there were approximately 314 thousand sectors in Brazil.

Ireland

In the Republic of Ireland, the Central Statistics Office (CSO), established in 1949, organises the census.[6] Beginning from the 2011 census, the CSO website has made available "Small Area Population Statistics" (SAPS) for each "small area", a subdivision of an electoral division (ED) defined by Ordnance Survey Ireland constrained by natural landscape features.[7] Formerly main roads also constrained the borders but this was changed to increase data privacy.[7] A small area has a minimum of 65 and average of 90 households.[7] For the 2016 census there were 18,641 small areas.[8] The 2016 census also provides the population of each of 50,117 townlands, except those with a population of one sex or two people.[8]

From 1926 to 2006, the smallest unit of public reporting was the ED, then called "district electoral division" or "ward". (There were 3,409 EDs in 2016.[8]) Until 1911, the smallest reported unit was the townland in rural areas and the ward in urban areas. Subsequently, townland data was available on application to the CSO. All of the aforementioned are legally defined administrative units, although with no local government functions. From 1996 to 2006, "census enumeration areas" were included in data made available on request for areas within the five county boroughs but not the 29 administrative counties. A census enumeration area was the area covered by a single enumerator, and had an average of 330 households.[9] This data has since been published online.[10]

New Zealand
Main article: Mesh blocks

In New Zealand census tracts are known as meshblocks, or mesh blocks, and are defined by Statistics New Zealand as being "the smallest geographic unit for which statistical data is collected and processed by Statistics New Zealand". It is a defined area, varying in size from part of a city block to large areas of rural land. Each of these borders another to form a network covering the whole country including inlets and coasts, and extending out to the 200 mile economic zone. Meshblocks are added together to "build up" larger geographic areas such as area units and urban areas. They are also used to draw up and define New Zealand electorates and local authority boundaries.[1]

United Kingdom
See also: ONS coding system

British census tracts were first developed in the city of Oxford. The Inter-University Census Tract Committee was formed in 1955[11] and Oxford was divided into 48 tracts with an average population of 2,645 each.[12] The Registrar General, however, opted for enumeration districts containing less than 1,000 people on average, rather than adopting census tracts.[11] While tracts composed of enumeration districts were later developed, these were not extensively used.[13] Census tracts have, however, been constructed and used by British demographers.[14] The Office for National Statistics now uses enumeration districts only for the collection of data, with output areas used as the base unit in census releases.[15]

United States

The concept of the census tract was first developed in the United States. In 1906, Dr. Walter Laidlaw originated the concept of permanent, small geographic areas as a framework for studying change from one decennial United States Census to another in neighborhoods within New York City.[16] For the 1910 Census, eight cities—New York, Baltimore, Boston, Chicago, Cleveland, Philadelphia, Pittsburgh, and St. Louis—delineated census tracts (then termed ‘‘districts’’) for the first time. No additional jurisdictions delineated census tracts until just prior to the 1930 Census, when an additional ten cities chose to do so. The increased interest in census tracts for the 1930 Census is attributed to the promotional efforts of Howard Whipple Green, who was a statistician in Cleveland, Ohio, and later the chairman of the American Statistical Association's Committee on Census Enumeration Areas. For more than 25 years, Green strongly encouraged local citizens, via committees, to establish census tracts and other census statistical geographic areas. The committees created by local citizens were known as Census Tract Committees, later called Census Statistical Areas Committees.

The map of California shows both the county divisions (in black outline) and 2010 census tract divisions (in pink outline) for reference in understanding the relative size of census tracts. Urban areas have many more census tracts due to higher populations. The inset map shows a zoomed-in version of Ventura, Los Angeles, and Orange counties.

After 1930, the Census Bureau saw the need to standardize the delineation, review, and updating of census tracts and published the first set of census tract criteria in 1934. The goal of the criteria has remained unchanged; that is, to assure comparability and data reliability through the standardization of the population thresholds for census tracts, as well as requiring that their boundaries follow specific types of geographic features that do not change frequently. The Census Bureau began publishing census tract data as part of its standard tabulations beginning with the 1940 Census. Prior to that time, census tract data were published as special tabulations.

For the 1940 Census, the Census Bureau began publishing census block data for all cities with 50,000 or more people. Census block numbers were assigned, where possible, by census tract, but for those cities that had not yet delineated census tracts, ‘‘block areas’’ (called ‘‘block numbering areas’’ [BNAs] in later censuses) were created to assign census block numbers. Starting with the 1960 Census, the Census Bureau assumed a greater role in promoting and coordinating the delineation, review, and update of census tracts. For the 1980 Census, criteria for BNAs were changed to make them more comparable in size and shape to census tracts. For the 1990 Census, all counties contained either census tracts or BNAs.

Census 2000 was the first decade in which census tracts were defined in all counties. In addition, the Census Bureau increased the number of geographic areas whose boundaries could be used as census tract boundaries. It also allowed tribal governments of federally recognized American Indian tribes with a reservation and/or off-reservation trust lands to delineate tracts without regard to State and/or county boundaries, provided the tribe had a 1990 Census population of at least 1,000.[17]

Census tracts are also used by the Small Business Administration to define boundaries of HUBZones.

References
  1. "Meshblock (Concept)". Statistics New Zealand. 2 February 2016.
  2. "Census Tracts and Block Numbering Areas". U. S. Census Bureau. 2000-04-19. Retrieved 2007-12-05.
  3. Domínguez-Berjón, Felícitas; Borrell, Carme; López, Rosario; Pastor, Vicente (2005). "Mortality and socioeconomic deprivation in census tracts of an urban setting in Southern Europe". Journal of Urban Health. 82 (2): 225–236. doi:10.1093/jurban/jti047. PMC 3456560. PMID 15888637.
  4. "U.S. Census Bureau definition". Archived from the original on 2017-05-13. Retrieved 2017-10-19.
  5. IBGE. "IBGE | censo 2010 | materiais | guia do Censo | operação censitária". censo2010.ibge.gov.br (in Portuguese). Retrieved 2018-06-01.
  6. Seanad Éireann (17 June 1993). "Statistics Bill, 1993: Second Stage". Seanad Éireann debates. Houses of the Oireachtas. Retrieved 8 January 2019.
  7. "Small Areas Ungeneralised". data.gov.ie. Ireland. 2015. Retrieved 8 January 2019.
  8. "Census 2016 Small Area Population Statistics". Ireland: Central Statistics Office. Retrieved 8 January 2019.
  9. "2006 Census Enumeration Areas Boundaries". Central Statistics Office. Ireland. Retrieved 8 January 2019.
  10. "Census Reports 1821-2006". Central Statistics Office. Ireland. Retrieved 8 January 2019.
  11. Longley, Paul; Clarke, Graham (1996). GIS for Business and Service Planning. New York: John Wiley & Sons. pp. 80–81. ISBN 0-470-23510-1.
  12. Robson, Brian Turnbull (1969). Urban Analysis: A Study of City Structure with Special Reference to Sunderland. Cambridge: Cambridge University Press. pp. 44. ISBN 0-521-07272-7.
  13. Exeter, Daniel J.; Boyle, Paul; Feng, Zhiqiang; Flowerdew, Robin; Schierloh, Nick (2005). "The creation of 'Consistent Areas Through Time' (CATTs) in Scotland, 1981–2001" (PDF). Population Trends. 119: 28–36. Archived from the original (PDF) on 2011-06-05. Retrieved 2009-10-25.
  14. "Tracts – Information page". Social and Spatial Inequalities Group, Department of Geography, University of Sheffield. Archived from the original on 2009-02-25. Retrieved 2009-10-25.
  15. "Beginners' guide to UK geography: Census geography". Office for National Statistics. 2007-10-30. Archived from the original on 2011-06-04. Retrieved 2009-10-25.
  16. Krieger, Nancy (2006). "A century of census tracts: Health & the body politic (1906–2006)". Journal of Urban Health. 83 (3): 355–361. doi:10.1007/s11524-006-9040-y. PMC 2527201. PMID 16739037.
  17. "Census Tract Program for the 2010 Decennial Census—Final Criteria" (PDF). Federal Register. U. S. Census Bureau. 2008-05-14. Retrieved 2008-10-14.
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