• Community Services (retired), Standard 21/05/2010
• Early Childhood, Standard 21/05/2010
• Health, Standard 04/08/2016
• National Health Performance Authority (retired), Retired 01/07/2016

Australian Institute of Health and Welfare

The official measure of the population of Australia is based on the concept of usual residence. 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. It includes usual residents who are overseas for less than 12 months. It excludes overseas visitors who are in Australia for less than 12 months. Estimates of the Australian resident population are generated on a quarterly basis by adding natural increase (the excess of births over deaths) and net overseas migration (NOM) occurring during the period to the population at the beginning of each period. This is known as the cohort component method, and can be represented by the following equation:

P_t+1 = P_t + B - D + NOM, where:

P_t = the estimated resident population at time point t

P_t+1 = the estimated resident population at time point t+1

B = the number of births occurring between t and t+1

D = the number of deaths occurring between t and t+1

NOM = net overseas migration occurring between t and t+1.

For state and territory population estimates, an additional term is added to the equation representing net interstate migration (NIM) occurring between t and t+1, represented by the following equation:

P_t+1 = P_t + B - D + NOM + NIM.

The estimates by age of the population of Australia and the states and territories at the date of the Census are derived from the Census counts by place of usual residence, by adjusting for under-enumeration and adding the number of Australian residents estimated to have been temporarily overseas at the time of the Census.

Post-censal population estimates are obtained by advancing the previous year's estimates to the next year by subtracting deaths and adding births and net estimated interstate and overseas migration. After each Census, estimates for the preceding intercensal period are revised by incorporating an additional adjustment (intercensal discrepancy) to ensure that the total intercensal increase at each age agrees with the difference between the estimated resident populations at the two respective Census dates.

Net overseas migration

Conceptually, NOM is the difference between permanent and long-term arrivals, and permanent and long-term departures. Estimates of NOM are derived from information provided on incoming and outgoing passenger cards, as well as other data supplied by the Australian Government Department of Immigration and Border Protection. Data on the intended duration of stay of overseas visitors arriving in Australia and the intended duration of absence of Australian residents travelling overseas are used to determine the numbers of permanent and long-term arrivals, and permanent and long-term departures. Passenger card data are also used to calculate migration adjustments and determine the state and territory distribution of NOM. The processes of adjusting movement data on travellers' stated intentions to reflect their actual behaviour are complex, and depend upon the amount and type of movement data available at a particular point in time.

Australian Institute of Health and Welfare

Population Estimates: Concepts, Sources and Methods, 2009 (ABS cat no 3228.0.55.001)

Australian Demographic Statistics (ABS cat no 3101.0)