The projections cover eight possible future scenarios that reflect different combinations of assumptions about future migration and future household transition probabilities. These scenarios are described below in Table 2. The assumptions that do not vary across the scenarios are set out in Table 1.
| Input | Assumption |
|---|---|
| Fertility | Age –specific fertility rates were calculated for each region for the year, 2006. These rates were assumed to remain constant throughout the projection period. McDonald and Kippen (2008) have suggested that constant fertility is the most likely result for Australia in the next decade. |
| Mortality | Abridged life tables for each region were calculated from 2001-06 mortality data. The rate of change in Australian expectations of life from 1991 to 2006 was obtained and annualised. This annual rate of change was then applied year by year to the expectation of life in each region with the rate of change being reduced by five per cent each year. |
| Dwelling Type | The 2006 distributions of dwelling type by region, type of household and age of the reference person were assumed to remain constant throughout the projection period. |
| Tenure Type | The 2006 distributions of tenure type by region, dwelling type, type of household and age of the reference person were assumed to remain constant across the projection period. |
| Scenario | Migration | Household transition probabilities |
|---|---|---|
| 1 | Age and sex specific net migration rates (international and internal combined) for each region as observed in the 2001-06 period are maintained. | Age, sex and region specific probabilities for the period, 2001-06, are assumed to remain constant across the projection period. |
| 2 | International migration is set at 230,000 per annum from 2008 onwards. Shares to States and Territories of international migration and rates of internal migration are equated to those used by ABS in its medium projection. | Same as Scenario1 |
| 3* | International migration is set at 180,000 per annum from 2008 onwards. Shares to States and Territories of international migration and rates of internal migration are equated to those used by ABS in its medium projection | Same as Scenario 1 |
| 4 | The assumptions here are the same as Scenario 3 except that, over time, increasingly higher proportions of international migrants are assumed to go to Queensland and Western Australia (see Table 3) | Same as Scenario 1 |
| 5 | Same as Scenario1 | The annualized rate of change in transition probabilities from 1996-2001 to 2001-06 is continued forward but reduced at the rate of 5% per annum until 2015. From 2016 to 2012, the rates remain constant. |
| 6 | Same as Scenario 2 | Same as Scenario 5 |
| 7 | Same as Scenario 3 | Same as Scenario 5 |
| 8 | Same as Scenario 4 | Same as Scenario 5 |
* Note Scenario 3 has the same assumptions as the 2008 ABS population projections (medium).
Table 3 indicates the variations across the scenarios in the shares of net international migration going to each state and territory.
| State or Territory | Shares of net international migration (%) | |
|---|---|---|
| ABS assumption: Scenarios 1-3 and 5-7 |
Alternative assumption, achieved by 2021 by linear change from 2006: Scenarios 4 and 8 |
|
| New South Wales | 31.5 | 29 |
| Victoria | 26.5 | 24 |
| Queensland | 19.0 | 23 |
| South Australia | 6.5 | 5 |
| Western Australia | 14.5 | 17 |
| Tasmania | 0.8 | 0.8 |
| Northern Territory | 0.6 | 0.6 |
| A.C.T. | 0.6 | 0.6 |
With net overseas migration set at 180,000, the assumed levels of annual net migration for each geographic unit in 2021 are shown in Table 4 for Scenarios 3 and 7 compared with Scenarios 4 and 8.
| Region | Annual net migration (international + internal) | |
|---|---|---|
| Scenarios 3 and 7 | Scenarios 4 and 8 | |
| Sydney | 18467 | 14144 |
| Balance of NSW | 18233 | 18056 |
| Melbourne | 35595 | 31341 |
| Balance of Victoria | 5605 | 5359 |
| Brisbane | 23826 | 28105 |
| Balance of Queensland | 37874 | 40795 |
| Adelaide | 6376 | 3912 |
| Balance of South Australia | 2324 | 2088 |
| Perth | 23438 | 27479 |
| Balance of WA | 5152 | 5621 |
| Hobart | 839 | 839 |
| Balance of Tasmania | 101 | 101 |
| Northern Territory | 580 | 580 |
| ACT | 1580 | 1580 |
| South East Queensland* | 48693 | 57438 |
* South East Queensland includes the s
tatistical divisions of Brisbane, Gold Coast, Sunshine Coast and West Moreton and Toowoomba Regional Council (Cambooya Shire - Pt A, Crow's Nest Shire - Pt A, Jondaryan Shire - Pt A, Rosalie Shire - Pt A, and Toowoomba City).
In Victoria, South Australia, Western Australia and Tasmania, net migration is considerably higher for the capital cities than for the balances of state. In New South Wales, Sydney and Balance of NSW have similar levels of net migration while in Queensland, net migration to Brisbane is lower than net migration to the Balance of Queensland. In Queensland, this result is due to substantial growth in areas of South East Queensland outside of Brisbane. Interestingly, in numerical terms, net migration is very much higher to Melbourne than to any other capital city, although not nearly as high as migration to South East Queensland.