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Census geography


There is a geographic component to every stage of the census cycle, from consultation through collection, processing and dissemination. Users are consulted about the geographic concepts used by Statistics Canada and about various options for disseminating standard geographic data. Small geographic areas are defined and mapped in detail so that every dwelling can be located during the data collection phase. During the processing phase, the data collected by households are coded to the appropriate geographic areas in the hierarchy of geographic units used for dissemination. Finally, census data are disseminated by a variety of geographic areas, along with supporting reference maps and other geographic data products.

Water falls in violent cascade over a cliff.

To take full advantage of census data, users need to have a basic understanding of the geographic dimension of the data. Just as one can subdivide a population by sex or into age, income and occupation groups, one can subdivide a population by different geographic areas. The geographic areas used by the census range in size from provinces and territories down to dissemination blocks and are organized in a hierarchical model to show the nature of their relationships.

Hierarchical model of geographic areas

The geographic areas and their relationships are depicted in a hierarchy chart (Figure 20). Each box in the hierarchy chart represents one type of geographic area. The position of each type of geographic area in the chart shows how it can be subdivided or aggregated to form other geographic areas. For example, the 13 provinces and territories are subdivided into 308 federal electoral districts (federal ridings), which in turn are subdivided into 478,831 dissemination blocks. The lines joining the boxes in the chart show that there is a relationship between the geographic areas at one level and those at the next level. In general, this relationship is a 'one-to-many' relationship moving from top to bottom of the chart, and from bottom to top, the relationship is 'many-to-one'. Many areas at the lower level in the chart 'nest' or fit exactly into one area at the next level in the chart. Each 'branch' of the hierarchy shows that, in general, there is no relationship between the geographic areas in that branch and those in an adjacent branch. For example, the chart shows that dissemination areas (DAs) group together to form census subdivisions (CSDs); they also group together to form census tracts (CTs), but there is no relationship (no exact fit) between CSD boundaries and CT boundaries.

A particular branch in the hierarchy shows how one can carry out geographic analysis starting with the general and moving to the specific (a top-down approach). For example, one can start with Canada and then, within each province or territory, look at census divisions (CDs) and census subdivisions (CSDs). Or, using a bottom-up approach (building-block fashion), one can start by examining specific individual areas, CSDs for example, and comparing them with each other, within a particular CD, then within the province or territory, and eventually within the nation as a whole.

The section covering 'Administrative and statistical areas', found later in this chapter, briefly describes each of the geographic areas shown in the hierarchy chart. More detailed definitions are available in the 2006 Census Dictionary. To put these descriptions in context, the following section describes the significant changes made, since the last census, to the way in which Statistics Canada creates and maintains the geographic infrastructure.

Geographic databases

The geographic areas depicted in the hierarchy chart are incorporated into large geographic databases. The databases include a digital representation of the boundaries of these areas, as well as attribute data, such as the names and codes, which are necessary for uniquely identifying each area. The databases contain additional geographic features including the road network, various hydrographic features (lakes, rivers and coastal shorelines), and other selected visible features (for example, railroads and power transmission lines). The additional features also have associated attribute data, such as street names and address ranges.

As shown in Figure 20, the dissemination block is the basic geographic area that respects the boundaries of all other geographic areas at a higher level in the hierarchy. Each side of a dissemination block is called a block-face and, generally, address ranges are known for block-faces in larger urban centres.

Administrative and statistical areas

In Figure 20, geographic areas are depicted as being either administrative or statistical areas. Administrative areas are defined, with a few exceptions, by federal, provincial or territorial statutes, and are adopted for the purposes of the census. Statistics Canada, in cooperation with stakeholders, defines statistical areas for disseminating census data and complementing the structure of administrative regions. Table 1 shows the number of geographic areas by province and territory for the 2006 Census.

Provinces and territories are administrative areas that provide the first level of detail in the geographic hierarchy for Canada. All other administrative and statistical areas respect provincial and territorial boundaries (with the exception of nine statistical areas that cross provincial boundaries).

One of the administrative areas in the hierarchy is the federal electoral district (FED), an area represented by a federal Member of Parliament. The constitutional basis for the census originates from the requirement to apportion federal electoral representation based on population counts. Following the release of population counts from each decennial census, Canada's Chief Electoral Officer determines the number of seats in the House of Commons based on those census population counts. In the geographic hierarchy, the FEDs group together to form provinces and territories, and dissemination blocks are defined to respect the FED boundaries.

The geographic areas used for census data collection are slightly different than those used for dissemination. Data are not published using collection-oriented geographic areas and, therefore, are not represented in the hierarchy of geographic units used for dissemination (Figure 20). The geographic areas used for census data collection include the collection unit (CU), the collection block (COLB) and supervisory areas for each field operation. (See Figure C).

Figure C   Hierarchy of geographic units for collection, 2006 Census

Figure C   Hierarchy of geographic units for collection, 2006 Census

Many provinces and territories are already divided into smaller areas for regional and local government purposes. Counties, regional districts, regional municipalities, cities, towns, townships and Indian reserves are examples of subprovincial administrative areas. To manage the variation in statuses given to these areas between provinces and territories, Statistics Canada uses standard terms to refer to groups of similar status. For example, census division (CD) is the general term applied to areas established by provincial law that are intermediate geographic areas between the municipal and provincial/territorial levels.

Census divisions (CDs) represent counties, regional districts, regional municipalities and other types of subprovincial legislated areas. In Newfoundland and Labrador, Manitoba, Saskatchewan, Alberta, Yukon Territory, Northwest Territories and Nunavut, provincial and territorial law does not provide for these administrative geographic areas. Therefore, Statistics Canada, in cooperation with these provinces and territories, has created census divisions for the dissemination of statistical data. Next to provinces and territories, CDs are the most stable administrative geographic areas and are therefore often used in longitudinal analysis.

'Census subdivision' (CSD) is the general term for municipalities (as determined by provincial or territorial legislation) or their equivalents (for example, Indian reserves, Indian settlements and unorganized territories). There are 55 types of CSDs identified for the 2006 Census. Their boundaries and names can change from one census to the next because of municipal annexations, dissolutions and incorporations. The Standard Geographical Classification (SGC) is Statistics Canada's classification for the three types of administrative geographic areas discussed above: provinces and territories, census divisions (CDs), and census subdivisions (CSDs). The SGC provides unique numeric identification codes for these hierarchically-related geographic areas.

Three types of statistical areas are defined by grouping administrative areas to facilitate special data analysis: economic regions (ERs), census agricultural regions (CARs) and census consolidated subdivisions (CCSs).

Economic regions (ERs) are groupings of complete CDs (with one exception in Ontario). Prince Edward Island and the three territories each consist of one economic region. Economic regions are used primarily for analysis of regional economic activity.

Agricultural data programs use subprovincial areas known as census agricultural regions (CARs), also known as 'crop districts' in the Prairie provinces. Census agricultural regions are made up of groups of adjacent CDs. In Saskatchewan, CARs are made up of groups of adjacent census consolidated subdivisions (CCSs), but these groups do not necessarily respect CD boundaries.

Census consolidated subdivisions (CCSs) provide a level of geography between the CD and the CSD. A CCS is a grouping of adjacent CSDs. Generally, the smaller, more urban, CSDs are combined with larger surrounding CSDs. For instance, a town located within a surrounding township will be grouped together with the township to form a CCS. CCSs are relatively stable geographic units and can therefore be used for longitudinal analysis.

Photo: A lighthouse on a rocky shore.

Designated places (DPLs) are normally small communities or settlements that do not meet the criteria established by Statistics Canada to be a CSD (an area with municipal status) or an urban area. Designated places are created by provinces and territories, in cooperation with Statistics Canada, to provide data for submunicipal areas. The areas recognized as DPLs may not represent all places having the same status within a province, but they must respect CSDs and not overlap urban areas.

Most of Canada's vast land area is sparsely populated and, with each passing decade, a greater proportion of the total population is becoming urban. Based on rules that respect total population and population density, all land is defined by Statistics Canada as either 'urban' or 'rural'.

An urban area has a minimum population concentration of 1,000 persons and a population density of at least 400 persons per square kilometre. All territory outside urban areas is classified as rural. Taken together, urban and rural areas cover all of Canada. Urban areas are defined using population counts and population density data from the current census. The population density data are based on the dissemination block.

More than 80% of Canada's population lives in urban areas with a population of 10,000 persons or more. Urban-focused economies tend to expand beyond municipal boundaries in terms of shopping trips and commuter travel. In order to represent those geographic areas under the influence of a major urban area, Statistics Canada has created census metropolitan areas (CMAs) and census agglomerations (CAs), which are groupings of adjacent municipalities (CSDs) that are highly integrated with the central urban area, as measured by commuting flows derived from census place of work data.

Census metropolitan areas (CMAs) must have a total population of at least 100,000, of which 50,000 or more must live in the urban core. Census agglomerations (CAs) must have an urban core population of at least 10,000 persons.

'Urban core' is a large urban area around which a CMA or a CA is delineated. The urban core of a CA that has been merged with an adjacent CMA or larger CA is called the 'secondary urban core'. An 'urban fringe' includes all small urban areas within a CMA or CA that are not contiguous with the urban core of the CMA or CA. All territory within a CMA or CA not classified as an urban core or an urban fringe is called 'rural fringe'.

Photo:  Lake Louise, Alberta.

In census tabulations, urban population includes all the population living in the urban cores, secondary urban cores, and urban fringes of census metropolitan areas (CMAs) and census agglomerations (CAs), as well as population living in urban areas outside CMAs and CAs. Similarly, the rural population includes all the population living in rural fringes of CMAs and CAs, as well as the population in rural areas outside CMAs and CAs.

Census tracts (CTs) are small, relatively stable geographic areas within census metropolitan areas and larger census agglomerations (those with an urban core population of 50,000 or more in the previous census). A committee of local specialists (for example, planners, health and social workers, and educators) initially delineates census tracts in conjunction with Statistics Canada. Census tracts usually have a population of 2,500 to 8,000 (preferably close to 4,000), and boundaries that generally follow permanent physical features, such as major streets and railway tracks, and attempt to approximate homogeneous socio-economic characteristics at the time of creation. Census tract boundaries are generally held constant from one census to the next, so that they are comparable over time. A CT may be split when its population exceeds the target range, but normally it is done in such a way that the divided areas can be easily aggregated to equal the original CT boundary. Census tract boundaries must respect CMA, CA and provincial boundaries, but do not have to respect CSD boundaries.

Census metropolitan area and census agglomeration influenced zones (MIZ) is a concept applied to census subdivisions outside of CMAs and CAs to further differentiate this vast, largely rural area of Canada for statistical purposes. These non-CMA, non-CA census subdivisions are assigned to one of four categories according to the degree of influence (strong, moderate, weak, and no influence) that CMAs or CAs have on them. Census subdivisions are assigned a MIZ category, using commuting flow data from the resident employed labour force, derived from previous census place of work data census subdivisions with the same degree of influence tend to be clustered.

The Statistical Area Classification (SAC) groups census subdivisions (municipalities) according to whether they are a component of a CMA, a CA, a MIZ or the territories. The application of this classification to CSD data can help users study the diversity of non-CMA, non-CA areas of Canada.

The dissemination area (DA) is a small, relatively stable geographic unit composed of one or more dissemination blocks. It is the smallest standard geographic area for which all census data are disseminated. Dissemination areas cover all the territory of Canada. In most cases, DAs have a population of between 400 and 700, which helps avoid the need for data suppression. Dissemination area boundaries respect census subdivision and census tract boundaries; thus, they can be added together or 'aggregated' to create any of the other standard geographic areas above CSDs and CTs in the hierarchy.

The concept of 'locality' is supported to maintain a record of historical place names of former census subdivisions (municipalities), former designated places, and former urban areas, as well as the names of other entities, such as neighbourhoods, post offices, communities and unincorporated places. Localities are stored as points in the geographic database; therefore, their location relative to any standard geographic area is easily determined. These data are helpful for searching for a standard geographic area using the name of a place that is not part of Statistics Canada's standard geographic hierarchy. Census data are not available for localities, but are available for the standard geographic areas in which they are located.

The postal code is a six-character code defined and maintained by Canada Post Corporation solely for the purposes of sorting and delivering mail. Although shown as part of the hierarchy of geographic units for dissemination, the postal code is not, strictly speaking, a census geographic area. The first three characters of the postal code refer to the forward sortation area (FSA). The average number of households served by an FSA is 8,000 but the number can range from 0 to 60,000. Each postal code is associated with one or more delivery points. The average number of households served by a postal code is 19, but that number can range from 0 to 10,000.

There is no exact relationship between postal codes defined by Canada Post Corporation and the dissemination blocks or block-faces defined by Statistics Canada. Statistics Canada maintains a concordance file that makes it possible to approximately match the constantly changing postal code geography to the standard geographic areas used by the census. Users who have their own data organized by postal codes may request custom census data tabulations for areas based on the match provided by this concordance file.

The postal code is captured for all households from the address information provided by the respondent on the front page of the census questionnaire on Census Day. It is verified and then accepted, whether or not it is the same as the postal code assigned to that address by Canada Post Corporation. This makes it possible to tabulate census data by these postal codes, although results may be different than those obtained with the concordance file described above.

Postal codes should be used cautiously in lieu of geographic areas since they do not necessarily respect the boundaries of standard geographic areas. Postal codes captured from the census questionnaire may indicate the location of the mailbox where people wish to receive their mail, not necessarily the location of their dwelling.

Non-standard or user-defined geographic areas

The geographic areas described in the previous section are the standard areas used to organize and disseminate census data. In most cases, the standard geographic areas satisfy data user requirements for census data tabulations; however, there are also many users who want data tabulated for geographic areas that are not in the standard geographic hierarchy, depicted in Figure 20. Examples include school districts, health zones, and sales regions.

There are two basic types of such non-standard or 'user-defined' geographic areas: areas that are simple aggregations of standard geographic areas, and areas that do not match the standard geographic areas at all. An example of the first type could be sales regions for a census metropolitan area, where the sales regions are made up of one or more of the component municipalities. Examples of user-defined areas that do not match the standard geographic areas are market areas, school districts, and transportation and utility corridors. When clients want census data tabulated for non-standard geographic areas, they may turn to the Custom Area Creation Service provided by Statistics Canada (see the 'How census data are disseminated' section).

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