Dictionary, Census of Population, 2021
Figure 1.8
Reverse commuting flow rule

Figure 1.8 is a graphical representation of the reverse commuting (journey to work) flow rule (rule 3^{Note 1}) for delineating a census metropolitan area (CMA). A fictional grouping of 12 census subdivisions (CSDs), shown as polygons labelled 'A' through 'L,' represent the group of CSDs that could form a CMA.

All of CSD A and a small portion of the adjacent CSDs B and J are shaded to represent a population centre. This population centre also makes up the core of the CMA. Census subdivision D has a small, shaded polygon within it that identifies a population centre that is not part of the core and is therefore referred to as fringe.

Census subdivision D, which is adjacent to CSD B, has a reverse commuting flow with at least 100 commuters, greater than or equal to 50% employed labour force.^{Note 2} This is represented in the figure by an arrow that points from the delineation core (CSDs A and B) to CSD D. Census subdivision D is, therefore, included in the CMA.

A thick black line outlines the perimeter of CSDs A, B, C, D and excludes CSD K, leaving a hole to identify the new boundary of the CMA.

Two legends appear below the figure. The legend on the left identifies the symbols used in the figure to represent the boundaries of the CMA, CSD, population centre, core, fringe and the arrow indicating reverse commuting flow. The legend on the right distinguishes which CSDs are included in the CMA according to their inclusion criteria. For this figure, CSDs A and B are included under rule 1 (delineation core rule), CSD C is included under rule 2 (forward commuting flow rule) and CSD D is included under rule 3 (reverse commuting flow rule).

Source: Statistics Canada, 2021 Census of Population.