WA Tomorrow Population Forecast - Frequently Asked Questions

WA Tomorrow Population Report No. 12 (WA Tomorrow 12) is a series of trend-based population forecasts, by age and sex, for Western Australia from 2022 to 2036. These forecasts represent a best estimate of future population size and age-sex structure if trends in fertility, mortality and migration continue.

The WA Tomorrow population forecasts are produced by the Department of Planning, Lands and Heritage in collaboration with the Department of Treasury. The forecasts are produced on behalf of the Western Australian Planning Commission.  They are produced using the latest results from the five-yearly national Census of Population and Housing, and other data.

These population forecasts cannot foresee future events that change current trends. These include significant shifts in government policy (such as migration settings), natural disasters and epidemics.

WA Tomorrow 12 is being released in two parts. This initial release provides a whole-of-State forecast of the future population by age and sex to 2036. It also includes a forecast range (Bands A to E), indicating five probable futures. Bands A and B represent the lower forecasts, Band C is the median forecast and Bands D and E represent the higher forecasts.

The second WA Tomorrow release will comprise the sub-state population forecasts by age and sex to 2036 for Local Government Area and Statistical Area Level 2 (SA2) geographies.

WA Tomorrow 12 are the official Western Australian Government population forecasts to 2036. The forecasts are used across government agencies to plan for future service and infrastructure requirements where a change in the age and/or sex distribution needs to be considered. They are particularly important to health and education providers in planning future infrastructure and service requirements such as primary schools and hospitals.

WA Tomorrow forecasts use demographic data produced by the Australian Bureau of Statistics (ABS) as its basis. They are based on the best available data at the time. Key datasets include the Estimated Residential Population, Births by year, Deaths by year, and Overseas and Interstate arrivals and departures.

The model used to produce the age by sex forecasts is called the Cohort Component Model (CCM). The CCM is the most widely used method employed by demographers for preparing population projections. The forecast use assumptions on what is likely to happen in the future with regards to the demographic components of births, deaths and migration. These assumptions are based on an analysis of recent trends in these components.

The cohort component model uses the following demographic equation: 

New population =

Base population + births – deaths + in-migration – out-migration

WA Tomorrow is a medium-term trend forecast. Trend-based forecasts are better suited over the short to medium term. It is unreasonable to expect that these trends will prevail in the long term due to issues such as government policy and plans, economic cycles or natural disasters, which can change trends.

In order to provide a more realistic outlook on potential future population outcomes, WA Tomorrow uses probabilistic methods to produce a forecast range. This range is presented as five forecast bands ranging from low (Band A), medium-low (Band B), median (Band C), medium-high (Band D) and high (Band E). Band C is most often used by users as it represents the best estimate of the future population based on past trends.

The WA Tomorrow forecasts are distinct from targets or scenarios contained in other government plans or strategies such as Perth and Peel @ 3.5 million, which are based on a target population size and are generally longer term in their outlook.

WA Tomorrow 12 is a trend-based forecast, being what the future population is likely to be if current trends in fertility, mortality and migration continue.

A target can be a number over and above a forecast and is often aspirational. It helps with critically thinking about what planning and actions need to take place to achieve the target, especially if the forecast is considerably lower than the target.

A scenario can be a “what if” situation, for example “What happens when you change one or more of the components?”.

Other public and private entities also produce medium to long term population forecasts. The ABS and the Australian Government’s Centre for Population both produce WA population projections as a component of broader national forecasting exercises. Whereas these use nationally consistent methodologies, WA Tomorrow is better able to incorporate unique local factors and trends.

The WA Tomorrow 12 median forecast (Band C) is higher than the most recent projections published by the ABS (Population Projections, Australia, November 2023) and Centre for Population. These nationally based forecasts anticipate that the WA share of national net overseas migration will be close to that experienced over recent years, which were impacted by the closed borders during the pandemic. However, the WA Tomorrow 12 forecast anticipates that the future WA share of national net overseas migration will align more with the long-term, historic average.