Where a private dwelling was identified as occupied on Census Night but a Census form was not returned, the number of people normally in the dwelling and their key demographic variables are imputed. In these cases, the non-demographic variables are set to 'not stated' or 'not applicable'.
For these private dwellings, the hotdecking imputation process is performed. The non-responding dwellings are matched with donor dwellings and the count of people and their key demographic variables are copied from the donor record to the imputed record. The donor records must meet several conditions:
- they must be occupied private dwellings where a form was returned, contain a maximum of 6 persons, and all of those persons responded to the key demographic questions
- 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
- where available, they have similar sex and age group counts from administrative data.
For 2021 Census data, improvements were made to the imputation of non-responding private dwellings. Administrative data was used to help choose the donor dwellings with similar numbers of people and ages to those that did not respond. For example, administrative data may show that two males aged 30–34 years live in a house that was determined to be occupied of Census Night. We would then choose a donor house from the Census where administrative data also shows that there were two males aged 30–34 years. The key-demographic Census variables from this donor dwelling are copied across for the non-responding dwelling. This method aims to give us counts of people in the right age group rather than just choosing a random household in a similar dwelling type in the same geographical area.
Where a person in a non-private dwelling did not return a form, their demographic characteristics are copied from a randomly selected person in a similar non-private dwelling using Type of non-private dwelling (NPDD).