ARCHIVED – A description of the ethnic segregation/mixing within major Canadian metropolitan areas project
The construction of the maps
The geographic unit that data are mapped across can strongly influence both the patterns represented and the degree of detail depicted. The project relies on geographic boundary files produced by Statistics Canada and the ways that Statistics Canada makes data available. It is often desirable to have as much geographic detail as possible but creating maps at the dissemination area scale – the smallest geographic area that is readily available (population size approximately 800) – was rejected out of fear of losing too many respondents due to data suppression. Statistics Canada utilizes numerical thresholds to determine whether data can be made available for groups within a specified geographic area. The intent of the thresholds is to protect the anonymity of respondents and the confidentiality of responses. In general, the smaller the groups and/or geographic area, the greater is the likelihood that data could be suppressed. Although the threshold for data suppression depends on the variable under consideration, in general fewer than 10 respondents with a particular characteristic (e.g., a non-Canadian birthplace) results in suppression of results and a zero value being given to the group in a particular geographic area.
With these data dissemination restrictions in mind, and the small numerical size of many immigrant and visible minority groups in some cities, the basic geographic unit used to build maps for this project is the census tract. Census tracts are relatively small geographic areas that normally have a total population of between 2,500 and 8,000, with the average being 4,000. As such, they are often thought of as constituting a “neighbourhood” scale in terms of geographic coverage. Census tracts can be used for analysis purposes in census metropolitan areas and census agglomerations in which the population exceeds 50,000.
To assist map readers in interpretation of the maps, key features are indicated on each map: water bodies, expressways/major roadways, airport, and the boundary outlines and names of constitutive municipalities (census subdivisions) within each metropolitan area. In addition, census tracts that either have no population or a very tiny population are designated as “no population”. In some cases, data for particular tracts have been suppressed because the number of census respondents has been deemed insufficient by Statistics Canada. In building the maps, a great deal of attention has been given to the problem of small numbers exaggerating an individual group’s representation or degree of concentration, and every attempt has been made to minimize these problems. Consequently, when the total population (all groups) is less than 100, the census tract was treated as having ‘no population’.
The maps for individual groups also provide key information about numerical and relative size of the groups in order to facilitate a more meaningful interpretation of distributions and relative concentrations. Fundamentally, the ‘spatial concentration’ of a group of 5,000 people is a different social phenomenon relative to that for a group of 70,000 individuals. As an illustration, on each map for individual immigrant groups, the group’s numerical size and proportion of the total immigrant population in the city is indicated. The maps for each visible minority group also indicate the group’s numerical size, as well as the group’s proportion of the total population and total visible minority population. In short, each map provides key information that should assist readers in making meaningful interpretations or patterns.
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