Dictionary, Census of Population, 2021
Dissemination block (DB)

Release date: November 17, 2021


A dissemination block (DB) is an area bounded on all sides by roads and/or boundaries of Statistics Canada's standard geographic areas for dissemination. The dissemination block is the smallest geographic area for which population and dwelling counts are disseminated. Dissemination blocks cover all the territory of Canada.

Reported in

2021, 2016, 2011 and 2006 (dissemination block)

2001 (block)


Dissemination blocks are primarily an artefact of the road network. As such, the number of DBs created is a function of the timeliness and accuracy of the road network prior to the census. For the 2021 Census, the road network used for DB creation is up to date as of June 2021.

Highway medians, ramp areas and other irregular polygons may form dissemination blocks on their own. A morphological dissemination block is split to form two or more DBs wherever it is traversed by the boundaries of selected standard geographic areas. This makes it possible to aggregate dissemination block data to all higher level standard geographic areas. In 2021, DB boundaries were required to respect the following standard geographic areas: federal electoral districts (FEDs), census subdivisions (CSDs), census tracts (CTs), designated places (DPLs) and dissemination areas (DAs), health regions (HRs), local health integration networks (LHNs) and previous census population centres (POPCTRs).

In rural areas where the road network is sparse or even non-existent, the boundaries of collection blocks are used to avoid creating very large dissemination blocks.

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

PR-CD-DA-DB code Description
12 09 0103 002

Province 12: Nova Scotia
CD 09: Halifax
DA 0103
DB 002

59 09 0103 003

Province 59: British Columbia
CD 09: Fraser Valley
DA 0103
DB 003

Only population and dwelling counts are disseminated at the dissemination block level (with the dissemination area being the smallest standard geographic area for which characteristic data are disseminated). To ensure confidentiality, population counts are adjusted or rounded to a base of 5 for dissemination blocks having a population of less than 15.

Table 1.1 in the introduction shows the number of dissemination blocks by province and territory.

Refer to the related definitions of Census Division (CD); Census Subdivision (CSD); Census Tract (CT); Designated Place (DPL); Dissemination Area (DA); Federal Electoral District (FED); Population Centre (POPCTR) and Spatial Data Infrastructure (SDI).

Changes prior to the current census

In 2016, dissemination blocks (DBs) were required to follow three additional standard geographic areas: health regions (HRs), local health integration networks (LHNs) and previous census population centres (POPCTRs).

In 2006, the term 'dissemination block' replaced the term 'block.'

In 2001, the term 'block' was used.

Prior to 2001, households and their associated population and dwelling counts were geographically referenced to the enumeration area at the time of collection. For more information, refer to the Geography Working Paper Series – Introducing the Dissemination Area for the 2001 Census: An Update (Catalogue no. 92F0138MIE2000004).

Date modified: