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Post Enumeration Survey

The 2001 Census of Population and Housing was held on Tuesday, 7 August 2001. While every effort is made to ensure full coverage of people and dwellings in the census, inevitably small numbers of people will have been missed while others will have been counted more than once. In Australia more people are missed from the census than are counted more than once. The net effect of overcount and undercount is called net undercount.

To measure net undercount the ABS conducts a Post Enumeration Survey (PES) shortly after the census. Phil Browning, PES Group Leader at the Data Processing Centre and responsible for the processing phase of PES, explains that this is a sample survey (similar to the Monthly Labour Force Survey) that aims to provide an independent check of the census coverage (i.e. the extent of the undercount of Australia's population). The survey uses a sample of two-thirds of 1% of private dwellings in Australia.

In PES processing, the information collected in the PES is matched against corresponding census forms for those dwellings to determine whether a person has been counted more than once or not counted at all.

Results obtained in the PES are then used to add value to census counts by producing Estimated Resident Population (ERP) for Australia. ERP also includes residents temporarily overseas on Census night, and is backdated to 30 June 2001 using births, deaths, interstate and overseas migration data. ERP is the official ABS estimate of the Australian population, as used in allocating seats in parliament and distributing $35 billion of taxpayer funds. ERP based on the 2001 Census is due for release on 6 June 2002.

The ABS will produce data on three distinct population concepts based on the 2001 Census:

• Census counts by place of enumeration
• Census counts by place of usual residence
• Estimated resident population.