Sampling and Weighting Technical Report, Census of Population, 2021
1. Census data collection

During the data collection phase, the objective was to ensure that responses were obtained from all households in Canada. Field operations included listing dwellings, delivering invitation letters, determining the occupancy status of a dwelling and conducting interviews with non‑respondents.

1.1 Census delivery methods

For most private dwellings, respondents were asked to complete the questionnaire for themselves and all members of the household.

On May 3, 2021, all private dwellings in the mail-out (MO) areas (approximately 86% of private dwellings in Canada) received by mail a bilingual invitation letter to complete the questionnaire online. As in 2016, this letter contained a secure access code (SAC), the web address of the 2021 Census website, and a telephone number to allow the respondent to request a paper questionnaire if they preferred.

In list/leave (L/L) areas, which represent 7% of dwellings, census employees dropped off an invitation letter. L/L door-to-door delivery took place from May 3 to May 10, 2021. During the L/L operation, census employees listed all private dwellings in specific areas in their Visitation Record. The invitation letter had a SAC so that respondents could fill out the questionnaire online. Paper questionnaires were available upon request, using a toll-free number. In the L/L areas, it was necessary for the respondent to provide a mailing address to an operator in order for the paper questionnaire to be mailed.

In 2021, the mail-out with drop-off (MODO) methodology was introduced. MODO areas are those where all dwellings have addresses, the majority of which are mailable. In these mixed areas, those dwellings with a valid mailing address were mailed the regular MO material (just like the MO areas), while those that did not have a valid mailing address (that correspond to the civic address) received an invitation letter dropped at their door by a census employee. The MODO areas were introduced to maximize the number of census MO dwellings. MODO areas represent more than 6% of the dwellings, and allowed an increase in the use of the MO methodology to extend to about 90% of dwellings (82% in 2016).

Traditionally, the remaining dwellings, located in First Nations communities, Métis settlements, Inuit regions and other remote areas, are enumerated in person using canvasser methods. However, for the first time, in 2021, all First Nations communities, Métis settlements, Inuit regions and other remote areas were offered the opportunity to self-respond, provided it was operationally feasible (i.e., Internet was accessible in the community). Depending on the situation, the invitation letter of the MO, L/L or MODO methodology was used (with minor changes, e.g., the paper questionnaire option was not offered), followed by non‑response follow-up (NRFU). Households in areas where it was not operationally feasible to offer self-response completed their census questionnaire with a census employee (in person or over the phone). In 2021, dwellings in remote, northern and Indigenous communities represent about 1% of dwellings in Canada.

1.2 Census wave approach

Statistics Canada implemented a wave approach for the 2021 Census, which consisted of reminding Canadians to fill out their questionnaire by various contact methods at specific times throughout the collection period. It also encouraged respondents to complete their questionnaire online, while mitigating the risk of a decline in overall response by also offering other response options such as ordering a paper questionnaire. The following table outlines the key dates for the different waves.

In First Nations communities, Métis settlements, Inuit regions and other remote areas, depending on the situation, an invitation letter was delivered, by mail or in person, followed by non‑response follow-up, which started on May 14, 2021. Starting on August 3rd, a reminder letter was also delivered to non‑responding households in mail-out (MO) areas. If Internet was not available, questionnaires were completed in-person with a census employee from Statistics Canada starting on May 3, 2021.

Census Help Line

The Census Help Line, a free, nationwide, multilingual service, was available to all respondents. The toll-free number was advertised in all census communications materials.

1.3 Occupancy verification and follow-up activities for the 2021 Census

Apartment occupancy verification—The purpose of apartment occupancy verification (AOV) was to verify the occupancy status of all units in an apartment building through one management contact. The information was collected through a telephone interview with the contact person. This contact person could be the owner of the building, or the superintendent or the building manager, for instance. AOV is an important activity, because it helped produce a more accurate status of occupancy for these types of dwellings, and it reduced the workload of the census non‑response follow-up (NRFU) activity. AOV was conducted by Collection Support Unit operators from May 10 to 18, 2021.

Dwelling occupancy verification—For a sample of dwellings in mail-out (MO) areas, the status of occupancy was verified immediately before NRFU. Dwelling occupancy verification was conducted from May 21 to 28, 2021, to identify as many unoccupied or cancelled dwellings as possible close to Census Day, May 11, 2021, to remove these dwellings from the NRFU workload. The accuracy of the occupancy status is higher if identified closer to Census Day. This operation is independent from the AOV described above.

Non‑response follow-up—The purpose of NRFU was to obtain a completed questionnaire from all households that did not return a questionnaire. Follow-up was done via telephone or in-person visits. In list/leave areas, follow-up was conducted from May 21 to August 13, 2021, and in the mail-out and mail-out with drop-off areas from June 2 to August 13, 2021. In canvasser and reserve areas, NRFU was conducted from May 14 to September 24, 2021. If Internet was not available, questionnaires were completed in-person with a census employee starting on May 3, 2021.

1.4 Census of Population questionnaires

The majority of Canada’s population resides in private dwellings. For residents of private dwellings, census data are collected primarily by having one adult member of the household respond on behalf of the entire household through self-enumeration using an online questionnaire.

The census is the primary source of exhaustive demographic data in Canada. In 2021, the census questionnaires collected the following information:

Information collected from both short-form and long-form questionnaires:

• address
• names of usual residents
• date of birth, age
• sex at birth, gender
• relationships of household members (including marital or common-law status)
• knowledge of official languages
• languages spoken regularly at home and language spoken most often at home
• first language learned at home in childhood
• instruction in the minority official language
• Canadian military experience

Information collected from the long-form questionnaire only:

• activities of daily living
• place of birth of person/parents
• citizenship
• knowledge of non‑official languages
• ethnic or cultural origins
• First Nations, Métis or Inuk (Inuit) identity
• population groups
• Registered or Treaty Indian status
• membership in a First Nation or Indian band
• membership in a Métis organization or Settlement
• enrolment under, or beneficiary of, an Inuit land claims agreement
• religion
• mobility (one year and five years)
• education
• labour market activities
• language of work
• place of work and commuting
• expenditures (child care, child and spousal support)
• housing.

Most census data were collected using either the short-form or long-form questionnaires. In 2021, a sample of 25% of Canadian households received a long-form questionnaire.

1.4.1 Short-form questionnaire (forms 2A, 3A and 2C)

Form 2A:

This is the short-form questionnaire that is used to enumerate all usual residents of all private dwellings.

Form 3A:

This is the short-form questionnaire for individuals (similar to Form 2A), which is used to enumerate one person. It is delivered to usual residents in private dwellings who wish to be enumerated separately from other members of the household (e.g., roommates, boarders). It is also used to enumerate residents in some collective dwellings such as lodging and rooming houses for example.

Form 2C:

This is the short-form questionnaire for people living abroad (similar to Form 2A), which is used to enumerate residents who are temporarily overseas at the time of the census. For 2021, this includes Canadian government employees (federal and provincial) and their families, and members of the Canadian Armed Forces and their families.

1.4.2 Long-form questionnaire (forms 2A-L and 2A-R)

The long-form questionnaire complements the short-form questionnaire and is designed to provide more detailed information on people in Canada according to their demographic, social and economic characteristics.

Form 2A-L:

This is the most commonly used long-form questionnaire.

Form 2A-R:

This questionnaire is similar to Form 2A-L but is used in remote, northern and Indigenous communities only. It contains the questions from the long-form questionnaire with examples adapted for First Nations communities, Métis settlements, Inuit regions and other remote areas, as well as two additional questions on band housing. For 2021, there is a new question on band housing fees.

1.5 Collection response rate

The overall collection response rate for the 2021 Census of Population was 98.0%. This rate was calculated directly from the collection results, i.e., before data processing and data quality verification were completed. It represents the number of private dwellings for which a completed questionnaire was returned, divided by the number of private dwellings that enumerators coded as being occupied. The collection response rate for the long-form sample was 97.4% (for more information, see the 2021 Census of Population collection response rates).

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