Methods: Demography

Census of Population and Housing

The five yearly Census of Population and Housing is the primary source of basic population statistics, providing a total count of the population on Census night. Population counts can be provided according to place of enumeration or according to place of usual residence.

Estimated Resident Population (ERP)

In Australia the key population measure is the estimated resident population (ERP), which is based on the concept of a person’s ‘usual residence’ for a period of 12 months or more within Australia. The ERP in a census year is derived from the census count, with adjustments for estimated undercount and for Australian residents temporarily overseas on census night. Between censuses the ERP is updated using information on birth and death registrations from state and territory Registrars of Births, Deaths and Marriages, and overseas arrivals and departures data from the Australian Government Department of Home Affairs, as well as Medicare registration changes of address for modelling interstate migration.

Population estimates are referred to as preliminary, revised or final. Preliminary estimates are generally made available five to six months after the reference period. Revised estimates are generally published each September for the financial year ending in the previous year. Final estimates are published for the previous intercensal period after each census.

Preliminary estimates can be obtained from the Australian Bureau of Statistics publication: Regional population, published annually and containing estimates for the previous year.

Population projections

The projections for 2022 onwards have been produced by the NSW Department of Planning and Environment using a variety of best practice population projection methods including the cohort component method, housing unit method and the multi regional method. The cohort component model takes a population broken down by age groups and moves them forward in time using assumptions about when and how many people will die, how many babies women will have at certain ages, and how many people will move into and out of an area. The housing unit method distributes the population over time, modelling housing supply. This is used for the Greater Sydney area. The multi regional approach applies assumptions about age groups for NSW, regions and Statistical Areas Level 2 (SA2s). This takes a top-down and bottom-up approach constraining totals to the NSW totals. The details of the methods, processes and assumptions can be found on the NSW Department of Planning, Housing and Infrastructure website.

These projections have been used to calculate rates in indicators showing projected deaths and hospitalisations in NSW.

The year-to-year projections of population to 2041 by 5-year age group for the whole of New South Wales, Local Health Districts and Primary Health Networks are available in HealthStats NSW.

Projections by 5-year age group are available for LGAs from the NSW Department of Planning, Housing and Infrastructure website. The LGA projections are built on the SA2 outputs using a top-down approach.

References

Australian Bureau of Statistics. Regional population. Canberra: ABS. Latest release. Available at: https://www.abs.gov.au/statistics/people/population/regional-population

Australian Bureau of Statistics. Historical Population. Canberra: ABS, 2016. Available at: https://www.abs.gov.au/statistics/people/population/historical-population/latest-release

Department of Planning, Housing and Infrastructure. New South Wales State and Local Government Area Population Projections. Available at: https://www.planning.nsw.gov.au/Research-and-Demography/Population-Projections

Department of Planning, Housing and Infrastructure. 2022 NSW Population Projections - Technical Methods Paper. Available at: https://www.planning.nsw.gov.au/Research-and-Demography/Population-Projections/Projections-methodology