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NSW Department of Planning, Industry and Environment
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Trusted approach

Accurately projecting the likely future population means understanding the demographic processes that drive population change.


The Department’s approach has been independently developed by demographers incorporating best practice population projections methods. The primary method used is the Cohort-Component Method. This is widely considered the international gold standard for population projections.  

It is supported by a wide body of academic literature and evidence from its practical application around the world. All Australian state and territory governments use some form of Cohort-Component Method, and similar approaches are used by the Australian Bureau of Statistics, the United Nations, and other national statistical agencies internationally.


The cohort component method divides the population into cohorts or generations – by age and by sex – and models how the components of population change – births (fertility), deaths (mortality) and migration – affect each of the cohorts. In the NSW Population Projections, assumptions are based on analysis of historical trends from a range of data sources, any announced policies and local intelligence gained from consultation with regional local councils.


The population projections reflect announced policies and projects. Any policies which were yet to be announced, yet to go on exhibition or were on exhibition at the time of production are not included.  Examples of projects excluded from the projections include Special Activation Precincts (SAPs) at Parkes, Wagga Wagga and Snowy Mountains and unannounced locations of future metro stations in Greater Sydney.


This approach  reflects the fact that certain life events – like having a baby, moving interstate, or dying - are more (or less) likely at different stages of life, and that this can change over time. For example, women now generally have children, and fewer of them, at later ages compared to back in the 1950s and 1960s. 


For the Greater Sydney Region, the projections use an additional method known as the Housing Unit Method to distribute the projected population over time. Using this method to supplement the Cohort-Component Method is used by many other places, including New York City and the City of London. This method is particularly useful for modelling population growth in areas covered by the Department’s Housing Supply Forecast. This Forecast is a basis for predicting where future housing development will occur. 

Geographic base

The projections are be based on Local Government Areas (LGAs) as at 30 June 2019, with data based on the Australian Bureau of Statistics (ABS) Australian Statistical Geography Standard (ASGS) 2019 approximation to these definitions.


Underlying evidence

The projections assumptions are informed by extensive analysis of a range of datasets:

  • Fertility rates are based on historical birth data from the Australian Bureau of Statistics and supplemented with data from NSW, Queensland, Victoria and ACT Health agencies’ Perinatal Data Collections.
  • Mortality rates are based on the Australian Bureau of Statistics mortality data.
  • Interstate and Intrastate Migration are derived from the Census question “where did you live 5 years ago?” These data are combined with trend information from historical estimates of interstate migration available from the Australian Bureau of Statistics. The likelihood for people to move in to, or out of, an area is then applied to future populations.
  • Overseas migration assumptions have been informed by short term forecasts from the Commonwealth Treasury as presented in the Annual Budget process. These forecasts are based on the latest data from the Department of Home Affairs on visa grants, past overseas migration flows by visa group, existing migration policy decisions and official economic outlooks. Age profiles for both arrivals and departures are determined from ABS data on migration, including the 2016 Census.



We review the projections every four years against census results to determine how well they performed. At the NSW level, the margin of error at 20 years has been ±2%, ±3% for regional NSW and ±4% for Greater Sydney. This represents a high degree of confidence.


Before developing new projections, the department reviews the approach to existing projections and updates it to ensure that new projections reflect best practice.


2020 insights

For the first time, the Department of Planning, Industry and Environment and the NSW Government have also prepared an easy-to-read insights resource to provide commentary on the changes in population and community over the past 12 months and in between projection releases. View the 2020 insights.


More information

Download technical factsheets

Page last updated: 30/12/2020