WHY ARE POPULATION ESTIMATES REVISED?
Population estimates produced by the ABS are important inputs to the allocation of funds to States and Territories and are required less than 6 months after the reference period (31 December each year). The ABS uses the most recent figures available for estimating components of population growth even if more accurate data will become available later. Consequently the ABS revises quarterly population estimates in stages as additional information becomes available.
Whilst there are three main categories of estimate (preliminary, revised and final), there is potential for an estimate to be revised several times. All components of population estimates are susceptible to revision as new and more accurate data becomes available. In particular:
- There is an interval between the date of occurrence of births and deaths, and their date of registration with State and Territory Registrars. Due to the delays in registration, estimates of natural increase (ie births minus deaths) become more accurate over time.
- Estimates of net overseas migration are also refined with time and can only be finalised 12 months after the reference date when passenger card data enables an assessment of whether, in aggregate, individual migration intentions have been realised.
Over recent years revisions to net migration estimates have had greater impact than revisions to natural increase. Further, from August 2000 until late 2002 there has been disruption to the availability of complete overseas migration data due to delays in processing of passenger cards as a result of data capture and processing system changes by the Department of Immigration and Multicultural and Indigenous Affairs.
The series of revisions that usually occur and their timing are outlined in Attachment A.
- Incorporating the results of the latest Census including allowance for net undercount and residents temporarily overseas on Census night ensures that population estimates are based on the most recent complete count of the population.