QUALITY DECLARATION - SUMMARY
Preparation of Australia's migration estimates uses data sourced from a number of other institutional environments.
The ABS statistics on net overseas migration (NOM) are calculated using administrative data collected and compiled by the Department of Immigration and Border Protection (DIBP) under the authority of the Migration Regulations (Migration Act, 1958). At present, the main source of data on overseas migration is incoming and outgoing passenger cards, matched with data from passports and visa permits. Information from these three data sources are collected, compiled and matched together by DIBP and stored with movement records on their Travel and Immigration Processing System (TRIPS).
Estimates of net interstate migration (NIM) are calculated using administrative data on interstate changes of address advised to Medicare Australia and to the Department of Defence in the case of the military. The Medicare-based model used for generating post-censal estimates of interstate migration is largely superseded when new Census information becomes available.
Australian Bureau of Statistics (ABS) Census of Population and Housing data are used to determine a base population and provide information on overseas-born residents. For information on the legislative obligations of the ABS, financing and governance arrangements, and mechanisms for scrutiny of ABS operations, please see ABS Institutional Environment.
Migration estimates referred to here are a component of population change and therefore a key determinant of the accuracy of the estimated resident population (ERP). The ERP is the official measure of the population of Australia according to a usual residence population concept. It refers to all people, regardless of nationality or citizenship who usually live in Australia, with the exception of foreign diplomatic personnel and their families. For the purposes of NOM a person is regarded as a usual resident if they have been (or are expected to be) residing in Australia for a period of 12 months or more. As from 1 July 2006 this 12 months does not have to be continuous and is measured over a 16 month reference period. Estimates for NOM exclude the movement of operational aircraft and ship's crew.
The data provides information on the flows of migrants into and out of Australia and between the states and territories. It also provides an annual stock take of the number of overseas-born residents. The main demographic variables available for each are:
- Overseas migration - includes age, sex, country of birth and state and territory;
- Interstate migration - includes age, sex, and state and territory; and
- Overseas-born residents - includes age, sex and country of birth (state and territory is only available for Census years).
Prior to the annual release of Migration, Australia (cat. no. 3412.0) preliminary NOM and NIM data are published quarterly in Australian Demographic Statistics (cat. no. 3101.0). NIM and NOM made available within six months after the end of each reference quarter.
Commencing with data for September quarter 2011, final estimates for NOM are released quarterly and made available 21 months after the end of the reference period. In the case of NOM, final data are based on actual traveller behaviour.
Estimates of overseas-born residents at the Australia level are made available annually with the release of Migration, Australia (cat. no. 3412.0). At the state and territory level the estimates are made only once every 5 years after a Census when the country of birth can be obtained at the state level.
Final estimates for NIM are made available every 5 years after a Census and revisions are made to the previous intercensal period.
All migration data sources are subject to non-sampling error which can arise from inaccuracies in collecting, recording and processing the data. The ABS does not have control over any non-sampling error associated with data from DIBP, Medicare Australia and the Department of Defence.
Another dimension of non-sampling error is the fact that the measures of migration estimates become more accurate as more time elapses after the reference period. The trade-off between timeliness and accuracy means that a user can access more accurate data by using the revised or final data.
In recognition of the inherent inaccuracy involved in estimating migration, figures in text released by the ABS are rounded. While unrounded figures are provided in the detailed spreadsheets, accuracy to the last digit is not claimed and should not be assumed. All calculations are based on unrounded numbers.
Annual migration estimates for Australia are available from 1860 onwards. Australia's population by country of birth is available for various states for Census years since 1846 (eg: New South Wales) refer to Australian Historical Population Statistics (cat. no. 3105.0.65.001).
Migration estimates are used in calculating official population estimates. The concept of estimated resident population was introduced in 1981 and backdated to 1971 as Australia's official measure of population based on place of usual residence. Before the introduction of ERP, the Australian population was based on unadjusted Census counts on actual location basis. It is important to note this break in time series when comparing historical migration estimates.
Population estimates are referred to as either preliminary, revised or final. Preliminary estimates are made available within six months after the reference quarter. Revised estimates are published each quarter when each of the different components of population change (birth, deaths and migration) are revised. Final estimates are published for the previous five-yearly intercensal period after each Census. See paragraph 9 of the Explanatory Notes of Migration, Australia (cat. no. 3412.0) for further information on the current status of ERP and its components.
An improved method for calculating net overseas migration (NOM) was applied and has been used in compiling Australia's official population estimates from September quarter 2006 onwards. The key change is the introduction of a '12/16 month rule' for measuring a person's residency in Australia replacing the '12/12 month rule'. This change results in a break in time series therefore it is not advised that NOM data calculated using the new method is compared to data previous to this.
The Migration, Australia (cat. no. 3412.0) publication contains detailed Explanatory Notes, Technical Notes and Glossary that provide information on the data. More in depth information is available from a number of sources, they include:
Migration data is available free of charge in a variety of formats on the ABS website.
The most timely data for both NOM data and NIM data are available quarterly in Australian Demographic Statistics (cat. no. 3101.0). It is made available within six months after the end of each reference quarter. This includes the release of a PDF version of the publication; time series spreadsheets (Excel format) including both NOM & NIM data; and a data cube (SuperTable format) with quarterly interstate arrivals and departures data.
The Migration, Australia (cat. no. 3412.0) publication provides annual data and analysis and includes information on overseas-born residents at 30 June each year. This includes the release of an HTML version of the publication and a number of time series spreadsheets (Excel and ABS.Stat format). Additionally, the NOM and NIM data sets are also released every six months to update calendar and financial year data.