Dictionary, Census of Population, 2021
Aggregate dissemination area (ADA)

Definition

An aggregate dissemination area (ADA) is a dissemination geography created for the Census. ADAs cover the entire country and, where possible, have a population between 5,000 and 15,000 based on the previous census population counts. ADAs are created by grouping existing dissemination geographic areas, including census tracts (CTs), census subdivisions (CSDs) or dissemination areas (DAs). ADA boundaries respect provincial, territorial, census division (CD), census metropolitan area (CMA) and census agglomeration (CA) boundaries.

The intent of the ADA geography is to ensure the availability of census data, where possible, across all regions of Canada.

Reported in

2021 and 2016

Remarks

The 2021 Census represents the second official release of the ADA geography, and some ADA codes have changed from the previous census. The following points explain why some ADAs were assigned new codes:

• The number of geographic areas (the number of CT, CSD or DA building units) that form the ADA is different from the previous census.
• The code for at least one geographic area (CT, CSD or DA building unit) that form the ADA is different from the previous census.
• The type of geographic area (CT, CSD or DA building unit) that form the ADA is different from the previous census.
• For example, new CTs are created and thus replace the CSDs or DAs as the building unit for the ADA.
• The ADA was modified to respect the new limit of a CMA or CA.

Aggregate dissemination areas (ADAs) respect the following delineation criteria:

1. The ADAs cover the entire country and, where possible, have a population count between 5,000 and 15,000 (based on the population counts from the previous census). In order to meet the operational constraint of releasing population and dwelling counts for ADAs in the winter following the census year, the population counts used to delineate ADAs were taken from the previous census.
2. ADA boundaries respect provincial, territorial, census division (CD), census metropolitan area (CMA) and census agglomeration (CA) boundaries in effect for the current census.
3. ADAs are based on one of three 2021 Census dissemination geographic areas that are referred to as building units: census tracts (CTs), census subdivisions (CSDs) or dissemination areas (DAs).
• Within CMAs and CAs with CTs, adjacent CTs are grouped to meet the ADA population criteria.
• In areas without CTs (areas outside the CMAs and the largest CAs) where CSDs have a population less than 15,000, adjacent CSDs are grouped to meet the ADA population criteria.
• In areas without CTs where CSDs have a population greater than 15,000, adjacent DAs are grouped within these CSDs to meet the ADA population criteria.
4. Each Indian Reserve census subdivisions (CSD) and a small number of other areas where door-to-door canvassing occurred form their own separate ADA.
• For example: The CSD has a one-to-one relationship with the ADA it forms.

Aggregate dissemination area code

Each aggregate dissemination area is assigned a four-digit code. To uniquely identify each ADA within Canada, the province/territory (PR) two-digit code and the census division (CD) two-digit code are concatenated and precede the ADA code. For example:

Refer to the related definitions of Dissemination Area (DA), Census Tract (CT), Census Subdivision (CSD), Census Division (CD), Census Metropolitan Area (CMA) and Census Agglomeration (CA).

Changes prior to the current census

For the 2016 Census, a consultation was undertaken with provinces and territories, and participating municipalities across Canada prior to finalizing the ADA boundaries. During consultations, from June to October 2015, Statistics Canada asked for input on an initial set of ADA boundaries to determine if any modifications should be made.^{Footnote 1}

Note(s)