Census Post Enumeration Survey

The Census aims to accurately count the number of people in Australia on Census night. Since 1966, the ABS has run a Post Enumeration Survey (PES) shortly after the Census to independently assess the completeness of the Census count. PES results are used to determine how many people should have been counted in the Census, how many people were missed and how many were counted more than once or in error.

The PES is the largest household survey conducted by the ABS. A random sample of approximately 45,000 households participated in the 2021 PES. From this sample, the ABS collected information from over 117,000 people.

In 2021 the PES used a new public facing name, the Post Census Review (PCR), to better reflect the survey and its purpose in plain language. The ABS conducted the survey via a short interview over the phone or in-person. The survey asked basic demographic details as well as location on Census night. This information was used to determine if and where a person should have been counted in the Census. It also supported the matching of PES person records to Census records to establish the number of times they were actually counted.

The difference between the PES estimate of how many people should have been counted in the Census and the actual Census count (including imputed persons) is known as the ‘net undercount’. Historically more people are missed than over-counted, resulting in a positive net undercount.

The results of the PES can be found at 2021 Census Overcount and Undercount.