After Census data has been collected, we look at the small number of houses where no Census form was received and where Census field staff are still unable to work out whether the house was occupied (for the 2016 Census, this was about 3% of all houses).
We must decide whether these houses were empty on Census night, or whether the Census count should be adjusted to cover people who were missed. For the 2021 Census we will use administrative data to help with this decision.
First, we create indicators from administrative data for the houses where we need to make an assessment. Some of these are specific to a house, while some relate to a group of houses across a wider area. All administrative data is stored safely and securely, and household level data is always kept confidential by storing it without address information attached.
The administrative data we use includes government services data (Medicare, Centrelink and Tax Office data), electricity usage from energy distributors and information from the ABS Address Register. We also use data from the previous Census.
Table 1 shows the type of indicators we use to assess whether houses were empty or occupied. Indicators from government services data and the ABS Address Register relate to houses, while indicators from electricity usage and the previous Census are created for a group of houses across an area.
Indicators from electricity data are created at an area level to strengthen privacy (refer to Note 1 for more information about the use of electricity data). Although this information loses some precision when we use it at an area level, it still provides an important signal of occupancy because it is more up to date than government services data at the time of the Census. Government services data are updated more slowly and tend to be a better signal for whether a house is empty or occupied over the long-term.