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Data quality and confidentiality standards and guidelines (public): Confidentiality practices

Confidentiality adjustment for population and dwelling counts

The population counts of small dissemination blocks with low population counts may be adjusted to reinforce the confidential nature of the data. In fact, all dissemination block population counts less than 15 will be rounded to a base of 5. This adjustment, however, will be controlled. That is, aggregates (totals) of the adjusted population counts for dissemination areas (DA) will always be within 5 of the actual values. The control will be even tighter at the census subdivision (CSD) level. In fact, while always being within 5 of the actual values, the adjusted population counts and the actual values agree for a maximum number of census subdivisions. Finally, all census division adjusted population counts and actual values agree, which means that the population counts for all census divisions (CD) remain unchanged.

Confidentiality adjustment for Forward Sortation Area (FSA) population and dwelling counts

The population counts for FSAs less than 15 will be rounded to a count ending in '0' or '5' to reinforce the confidential nature of the data. This adjustment will be controlled at the province level.

Confidentiality adjustment for place of work counts

The place of work counts for census blocks are available on a custom basis. These counts will be adjusted to reinforce the confidential nature of the data. In fact, all census block counts for employed labour force having a usual place of work or worked at home will be rounded to a base of 5. This adjustment, however, will be controlled. That is, aggregates of the adjusted population counts for dissemination areas will always be within 5 of the actual values.

Confidentiality adjustment for daytime population counts

Daytime population counts will be determined by taking the population living in a specific area, adding in the workers who live elsewhere and commute into the area, and subtracting the workers who live in the area and commute out of the area. The number of workers will be based on persons in the employed labour force having a usual place of work or worked at home. Daytime population counts will be adjusted to reinforce the confidential nature of the data by controlled rounding of the counts to a base of 5.

Preventing disclosure

Prevention of direct or residual disclosure must also be addressed when determining product content. When assessing the potential for disclosure, a number of factors must be considered. The detail of individual variables, cross-classification of variables and the geographic level of the data will all contribute to the risk. For example, there may be no risk in producing households by number of rooms in the dwelling and detailed groupings of dwelling value showing various characteristics of the household members for large geographic areas. However, the risk of disclosure would increase for the lower levels of geography.

The most common method used for preventing disclosure is defining content that is appropriate for a given geographic level. Increasing population thresholds or applying manual suppression as needed are other methods that can be employed. Since these are typically product-specific requirements, they are not part of the automated suppression systems.

Census of Agriculture tabulations

Census of Agriculture and Census of Population 2B (long form) data are matched using geographic information and the age and sex of farm operators. Match rates are about 95% and weighting is performed to account for non-matches. Data are available for all members of households where a farm operator resides.

Census of Agriculture data include farm type, farm sales, area of crops and numbers of livestock while the Census of Population provides socioeconomic data, including education, income and occupation of families and household members. Pre-planned standard products are produced at the province level only. Some multidimensional tables are available in pre-planned products with the usual being two or three dimensions.

Custom products are available at subprovincial levels based on aggregations of weighted areas, where 5,000 persons is the usual population threshold, although it can go as low as 2,500. The data are random-rounded and low-bounded to ensure confidentiality. Suppressions are done manually if cells are below a specified size.

All verification of tabulations is done internally by Census of Agriculture staff. There is a group responsible for reviewing all agriculture-population data before release.

Public use microdata files (PUMF)

The 2001 PUMF product consisted of a series of files based on different focuses: individuals, families and households. Each file contains approximately 3% of the Canadian population. The recommendation for the 2006 PUMF product is an individual file based on the individuals, families and households focuses.

Microdata files are unique among census products in that they give users access to non-aggregated data. This makes PUMF a powerful research tool. The files contain a large number of variables. Users can group and manipulate these variables to suit their own data and research requirements. Tabulations not included in other census products can be created, or relationships between variables can be analyzed using various analytical tools.

The census public use microdata files (PUMF) provide quick access to a comprehensive social and economic database about Canada and its people. They consist of samples of anonymous responses to the census long questionnaire. The PUMF files contain statistical information about Canadians, the families and households to which they belong and the dwellings in which they live.

Statistics Canada has to protect the confidential information that it collects. Owing to the very nature of a microdata file, various measures are taken to fulfil this commitment. The Microdata Release Committee reviews all requests for release of microdata.

Data for small geographic areas are not available in these files. The user will find information only for selected census metropolitan areas, the provinces and the territories. The breakdown of some sensitive variables was reduced for the Atlantic region. Some of the values of sensitive variables were suppressed because their combination could have been used to identify a person, a family or a household. Also, in 2001, the income variables were subjected to reduced low, and high, income limits. This will require review for 2006.

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