Everyone in Australia at Census time needs to be counted in the Census, excluding foreign diplomats and their families, no matter where they may be sleeping on Census night. To achieve this, the ABS has developed a strategy to obtain the best possible enumeration of people, no matter where they sleep. Some aspects of this strategy include liaising with service providers and engaging specialised field staff to count people sleeping rough on a special interview based form, and providing the ability for people to respond to the usual residence question as 'none' if they have no usual residence. Estimates of homelessness based on the 2021 Census will be released in 2023.
The primary imputation method used for the Census is known as 'hotdecking'. Other imputation processes use probability methods. In general the hotdecking method involves locating a donor record and copying the relevant responses to the record requiring imputation. The donor record will have similar characteristics and must also have the required variable(s) stated. In addition the donor record will be located geographically as close as possible to the location of the record to be imputed. The match must occur within the same Capital City or Balance of State.
The methodology for imputation is tailored to two situations. Firstly, where no Census form has been returned and secondly where a partially completed form was returned.
No Census form returned - private dwelling: Where a private dwelling was identified as occupied on Census night but a Census form was not returned, the number of males and females normally in the dwelling and their key demographic variables require imputation. In these cases, the non-demographic variables are set to 'Not stated' or 'Not applicable'.
For dwellings where the number of males and females is unknown, two imputation processes are performed. Initially, these records have their number of males and females imputed using hotdecking. Then a second imputation (also using hotdecking) is run to impute the key demographic variables for the newly created person records.
To hotdeck the number of males and females, the donor records must meet several conditions:
- they must be occupied private dwellings where a form was returned and contain a maximum of 6 persons
- they must have a similar Dwelling Structure (STRD) and Dwelling Location (DLOD) to the record to be imputed
- they must be located geographically as close as possible to the location of the record to be imputed
The number of males and females are the only data copied from the donor record in the first hotdecking process.
In the next process, the records which have just had their number of males and females imputed, are subjected to the same hotdecking process as those records where the number of males and females had been ascertained.
This hotdecking process imputes the key demographic variables. Again the donor records must meet several conditions:
- they must be records where everyone within the dwelling provided all their demographic characteristics
- they must have similar Dwelling Structure (STRD) and Dwelling Location (DLOD)
- they must have identical counts of males and females and
- they must be located geographically as close as possible to the location of the record to be imputed.
The key demographic variables are then copied from the donor records to the records requiring imputation
No Census form returned - Non private dwelling: Where a person in a non-private dwelling did not return a form, their demographic characteristics are copied from another person in a similar non-private dwelling using Type of non-private dwelling (NPDD).
Census form returned: Where a form was returned, some or all of the demographic characteristics may require imputation. Characteristics are imputed using a combination of hotdecking and probability techniques.
See also Derivations and imputations.
A household is defined as one or more persons, at least one of whom is at least 15 years of age, usually resident in the same private dwelling.
For Census purposes, the total number of households is equal to the total number of occupied private dwellings as a Census form is completed for each household from which dwelling information for the household is obtained.
The Census household form (online or paper) is the primary means for collecting Census data and is used in all private dwellings. The household form records details about the dwelling and characteristics of people in the dwelling. It records details of up to six people on the paper form and up to 25 people on the online form. Extra forms are used if there are more people than this.