Dictionary, Census of Population, 2021
Dissemination area (DA)

Release date: November 17, 2021


A dissemination area (DA) is a small, relatively stable geographic unit composed of one or more adjacent dissemination blocks with an average population of 400 to 700 persons based on data from the previous Census of Population Program. It is the smallest standard geographic area for which all census data are disseminated. DAs cover all the territory of Canada.

Reported in

2021, 2016, 2011, 2006 and 2001


For 2021, dissemination area (DA) boundary updates were undertaken where census tract and census subdivision boundaries were modified. In addition, a number of user-defined DA updates were completed based on the results of outreach to local specialists (for example, municipal planners and others).

Dissemination area rules

Dissemination areas respect several delineation criteria designed to maximize their usefulness for data analysis and to meet operational constraints.

  1. Dissemination area (DA) boundaries respect the boundaries of census subdivisions and census tracts.
  2. Apart from following census subdivision and census tract boundaries, DA boundaries usually follow permanent and visible features on the ground, such as roads, railways, water features and power transmission lines. A small number of DA boundaries also follow imaginary lines, such as street extensions, utility or transportation easements, and property lines.
  3. Dissemination areas are uniform in terms of population size, which is usually targeted from 400 to 700 persons to avoid data suppression. DAs with lower population counts, including zero population, may result in order to respect the boundaries of census subdivisions and census tracts or at the request of local specialists. DAs with higher population counts may also result.
  4. Dissemination areas are delineated based on the block population counts from the previous census due to operational constraints.
  5. Dissemination areas are compact in shape, to the extent possible while respecting the above criteria. They cannot be in multiple parts.

Dissemination area codes

Each dissemination area (DA) is assigned a four-digit code. In order to uniquely identify each DA in Canada, the two-digit province/territory (PR) code and the two-digit census division (CD) code must precede the DA code. For example:

PR-CD-DA codeDescription
12 09 0103Province 12: Nova Scotia
CD 09: Halifax
DA 0103
59 09 0103 Province 59: British Columbia
CD 09: Fraser Valley
DA 0103

When dissemination areas were first created, geographic proximity was embedded in the DA code by assigning DA codes in a serpentine manner within each census division. As DAs evolve, this coding structure cannot be maintained. Therefore, DA codes can no longer ensure geographic proximity. A DA code is changed when the DA undergoes a boundary change that impacts the population or dwelling counts.

Table 1.1 shows the number of dissemination areas by province and territory.

Refer to the related definitions of Census Subdivision (CSD); Census Tract (CT) and Dissemination Block (DB).

Changes prior to the current census

Previous to 2016, the number of dissemination blocks that were included in a dissemination area was limited to 99 due to operational constraints. This is no longer a constraint for the 2016 Census.

For 2011, dissemination areas (DAs) were defined as needed, rather than being completely re-delineated. This was to help ensure the comparability of data with previous censuses. To do this, planners located in areas with census tracts were surveyed for their input regarding the delineation of DAs that experienced high population growth between the 2001 and 2006 Censuses or that exceeded the DA maximum population limit. Other user-defined DA updates were accepted in areas where the DA structure either changed substantially between 2001 and 2006 as a result of automated delineation or simply did not provide users (local area experts) with relevant data since the DAs were not representative of their communities. The implementation of both of these types of user-defined updates eliminated the requirement for a fully automated delineation, which was used in previous censuses.

In 2006, dissemination areas (DAs) were delineated outside of census metropolitan areas (CMAs) and census agglomerations (CAs) using an automated area delineation system. Within CMAs and CAs that contained census tracts (CTs), DAs were kept relatively stable since the previous census. Some DAs in these areas were adjusted to respect changes to CT, CA, and CMA boundaries.

In 2001, the DA was a new standard geographic area. It replaced the enumeration area (EA) as a basic unit for dissemination. The 1996 population counts were used to delineate the DAs, mainly in blockface geocoding areas of CMAs and those CAs that contained CTs. Everywhere else, the 2001 DAs were the same as the 2001 EAs used for data collection.

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