Dissemination block: Detailed definition

Warning View the most recent version.

Archived Content

Information identified as archived is provided for reference, research or recordkeeping purposes. It is not subject to the Government of Canada Web Standards and has not been altered or updated since it was archived. Please "contact us" to request a format other than those available.

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

Census years

2011, 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. It is not possible to have a road network reflecting exactly the situation on Census Day. For the 2011 Census, the road network used for DB creation is up-to-date as of fall 2010.

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, namely federal electoral districts (FEDs), census subdivisions (CSDs), census tracts (CTs), designated places (DPLs) or dissemination areas (DAs). This makes it possible to aggregate dissemination block data to all standard geographic areas.

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

Each dissemination block is assigned a two-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 DB code. For example:

Table - Examples of dissemination block codes
PR-CD-DA-DB code Description
12 09 0103 02 Province 12: Nova Scotia
CD 09: Halifax
DA 0103
DB 02
59 09 0103 02 Province 59: British Columbia
CD 09: Fraser Valley
DA 0103
DB 02

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 for dissemination blocks having a population of less than 15.

Table 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) and Spatial Data Infrastructure (SDI).

Changes prior to the current Census

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 Introducing the Dissemination Area for the 2001 Census: An Update(Catalogue no. 92F0138MIE2000004).

Date modified: