Demography: Understanding Preliminary, Revised and Final estimates.
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What is Preliminary data?
What is Revised data?
What is Final data?
Demography is the statistical study of human population in relation to their size, structure, distribution and the changes in them in response to birth, death and migration.
There are three key areas that affect population change: fertility, mortality and migration.
Demography has also other features of population study, such as marriage, divorce, social mobility, ethnicity, religion, family formation, income and education.
The Australian Bureau of Statistics (ABS) sources data relating to births, deaths and migration primarily from the Registrars of Births, Deaths and Marriages, the Department of Immigration and Citizenship (international migration) and Medicare Australia (interstate migration).
Population estimates are one of the major outputs in demography. Estimates are subject to revision over time. The latest available data is the most accurate at the time, but as time goes on, estimates become more accurate because there is more known data on which to base them. To meet the conflicting demands of accuracy and timeliness, the ABS produces preliminary, revised, and final estimates for the different categories of demographic data.
What is 'Preliminary data'?
Preliminary data is provided as an estimate of the population at a given point in time, as soon as possible after all births, deaths and migration data available at any given time is provided to the ABS. This data provision occurs on an ongoing basis and the ABS aims to release preliminary estimates within 6 months after the reference quarter. For example, data for the September Quarter of any given year is generally released about end of the March of the following year.
What is 'Revised data'?
As registrations of births and deaths can occur up to several months after the event, there are lags in some of these events actually being registered and, thus, the ABS having access to this data. The ABS makes an estimate of the "missing" data and produces revised figures of the population. Delays in, or changes to, the processing of migration data can similarly affect initial estimates. Revised population data is released 21 months after the end of each financial year.
What is 'Final data?
Final population estimates are calculated after each Census of Population and Housing has been held (which occurs every five years), with the data being released about 22 months after the Census. For the reference period concerned, births and deaths that have been registered by the December Quarter in the year after the Census are taken to be final and are used in producing a final population estimate.
Footnotes or cell comments in a table alert users to the presence of preliminary, revised or final estimates.
Source: ABS publication 3101.0 - Australian Demographic Statistics, September 2009
Population Estimates: Concepts, Sources and Methods, 2009 (cat. no. 3228.0.55.001)