Aussies count – working out the official population figures


Like Count von Count, we here at the Australian Bureau of Statistics love counting. One of our most important statistics is knowing how many people live in Australia.

The official measure of Australia’s population is called Estimated Resident Population, or ERP. It can tell us how many people live in each local area, state or territory by age and sex.

ERP helps inform important decisions for the country like how much money each state and territory gets from GST revenue and the number of seats in Parliament. Recently, ERP has also been used to calculate COVID-19 vaccination rates.

Count Von Count
Count Von Count showing the increase in population from 13,067,265 people in 1971 to 25, 702,339 50 years later.

ERP is made using a mix of data from the Census and Post Census Review as well as births, deaths and migration records.

Components of ERP
The components of ERP are natural increase, overseas migration and internal migration. Natural increase is from state and territory registries of births, deaths and marriages. It's calculated by subtracting births from deaths. Overseas migration is when people move to and from Australia. It's calculated by estimating overseas migrant arrivals and departures from the most recent Census and data from the Department of Home Affairs. Internal migration is when people move within Australia. It's calculated from Census, Medicare and Department of Defence data.
Working out ERP
We work out the Estimated Resident Population by adding the Census, Post Census Review and number of Aussies Overseas together before factoring in births and deaths.

The five-yearly Census – which counts Australia’s households – is the basis for ERP. Feeding Census data into ERP makes it a richer source of information showing how many and where people live in Australia. By completing your Census in 2021, you just helped us work out the official Aussie population – not just for 2021, but all the way to 2026!

After the Census, we run a Post Enumeration Survey. This survey tells us how many people were missed, counted more than once, or counted by mistake. By comparing this to how many people were counted in the Census we get the total number of people who were in Australia on Census night.  

We then look at any birth, death and migration movements that happened between 30 June of the Census year and Census night to work out the population as at 30 June. We update ERP with births, deaths and migration numbers every year until the next Census when the process starts all over again!

The ERP is updated quarterly, yearly and every five years
The ERP is updated quarterly, yearly and every five years. State and territory level ERP is updated quarterly using admin data from population data sources like; birth registrations, death registrations, Medicare enrolment numbers and most recent Census information. Regional or substate populations are updated annually. Other parts of the ERP - like country of birth - are also updated annually between each Census. ERP is 'rebased' or updated every five years after every Census and Post Census Review. Aboriginal and Torres Straight Islander population estimates and country of birth by state and territory are also updated every five years.
Difference between the Census and ERP
There are some differences between the Census and ERP. Firstly, the Census is run every five years. It counts everyone in Australia on Census night, including visitors and it captures characteristics like income, education level and health. The ERP is Australia's official population estimate. It estimates the number of usual residents in Australia at the end of each quarter and uses a combination of data including Census information.

Count von Count would be thrilled to know he’s around the same age as ERP, which has just turned 50! Read more and watch this short animation to find out key population differences in the last 50 years. 

Count Von Count
Count Von Count is dressed in a party hat. Like the ERP he is also 50 years old!


*people in Australia – Australia's estimated resident population (ERP) includes all people who usually live in Australia (regardless of nationality, citizenship or visa status), with the exception of people present for foreign military, consular or diplomatic reasons. For the purposes of overseas migration, a person is added to Australia’s population if they have been (or expect to be) in Australia for 12 months or more. Likewise, an Australian resident is removed from the population if they leave Australia for 12 months or more. The 12 months does not have to be continuous and is measured over a 16-month period.


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