2902.0 - Census Update (Newsletter), Oct 2006  
ARCHIVED ISSUE Released at 11:30 AM (CANBERRA TIME) 18/10/2006   
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PES provides indispensable information

The Census of Population and Housing aims to accurately measure the number of people in Australia on Census Night, their key characteristics, and the dwellings in which they live.

While every effort is made to count each person and dwelling once in the Census, it is inevitable that in such a large operation, small numbers of individuals will be missed while others will be counted more than once. Usually more people are missed than overcounted in Australia, so the Census count of the population would be less than the true population. This difference is called net undercount.

To measure net undercount the ABS conducts a Post Enumeration Survey (PES) soon after the Census. This sample survey aims to provide an independent check of the of the Census coverage (i.e the extent of the undercount of Australia’s population). The survey uses a sample of around 38,000 dwellings (i.e. approximately half of 1% of private dwellings in Australia). In 2001, the PES estimated that the 2001 Census missed 1.8% of the people in Australia on Census night. However, rates of undercount can vary depending on factors such as sex, age, ethnicity (including Indigenous origin) and geographic location.

In PES processing, the information collected from PES dwellings is matched against corresponding Census forms for those dwellings to determine whether a person has been counted or missed in the Census, or counted more than once.

Estimates of net undercount are then used to:
• derive an estimate of the resident population for 30 June of the Census year
• provide users with an assessment of the completeness of Census counts, allowing them to take this into account when using Census information
• evaluate the effectiveness of Census collection procedures so that improvements can be made for future Censuses.

Accurate resident population estimates are required for a wide range of uses, including the allocation to states and territories of seats in the Federal House
of Representatives, the distribution of Commonwealth payments to states and territories, and demographic, social and economic studies.

More information about undercount and the methods used in the 2006 Post Enumeration Survey can be found in the Information Paper: Measuring net undercount in the 2006 Population Census, 2006 (cat. no. 2940.0.55.001), available for free from www.abs.gov.au.