Abbreviated as PES
The Post Enumeration Survey (PES) is a follow-up survey run by the Australian Bureau of Statistics after each Census. Its job is to find out how many people were missed or counted twice. The gap between the true count and the Census count is called the net undercount.
The ABS picks a sample of households soon after Census night. It checks whether each person filled in the Census form. By comparing the two sets of records, the ABS can estimate the size and pattern of the undercount.
In 2021, the net undercount was about 1%. This rate varied by age and state. Younger men and people in remote areas tend to be missed more often.
The ABS uses the PES results to adjust Census counts before working out the estimated resident population. Without this step, the official population figures would be too low.