Subnational Population Projections 2018-base Update

Projection assumptions for fertility, mortality, and migration are formulated after analysing short-term and long-term historical trends, information provided by local planners, and government policy. The Subnational population projections, projection assumptions, 2018(base)–2048 update table in NZ.Stat provides a summary of the low, medium, and high projection assumptions for each area. Main assumptions and changes from the previous 2018-base subnational population projections Deriving the projections involved a review of all projection assumptions. The following summarises the assumptions and main changes at the national level from the previous 2018-base projections released on 31 March 2021. The base population was 4.9 million at 30 June 2018 (2018–base population estimates). See Estimated resident population (2018–base): At 30 June 2018 for more information about the base population. The long-term median period total fertility rate (TFR) is assumed to be 1.65 births per woman, the same as in the previous median assumption. Age-specific death rates continue to decrease, but this decrease is more gradual compared with the previous 2018-base median projections. Life expectancy at birth for males will increase from 80.8 years in 2023, to 84.2 years in 2048. For females it will increase from 84.1 years in 2023, to 87.3 years in 2048. Life expectancy for 2048 is four months and five months lower respectively than the previous median assumptions. The long-term median annual net migration gain is assumed to be 25,000, the same as the previous projections. COVID-19 had a significant impact on international travel and migration in 2020–2021. With the easing of New Zealand border restrictions through 2022, net migration is assumed to gradually rise from the current negative levels. In the short term, median annual net migration is assumed to be -2,000 in the year ended June 2023, gradually rising to the long-term median net migration of 25,000 in 2026 and beyond. Geographic classification The population projections in this release are based on the regional council, territorial authority, and Auckland local board, classifications and boundaries at 1 January 2022. Fertility The assumed fertility rates are based on estimated births for each area during the period 2019–2022, with change between 2023 and 2048 consistent with the fertility assumptions from the National population projections: 2022(base)–2073. The median period total fertility rate (TFR) is assumed to be 1.70 in 2023 and gradually decrease to 1.65 by 2042, then stay at 1.65 births per woman throughout the rest of the projection period. In 2019–2023 the medium fertility assumption ranges from 1.00 birth per woman for Wellington city to 2.65 births for Kawarau district. In 2044–2048 the assumed total fertility rate for Wellington city remains the lowest at 1.00 births per woman, and Kawarau district has the highest, but this decreases to 2.50 births per woman. A sex ratio of 105.5 males per 100 females is assumed, based on the historical annual average at the national level. Mortality The assumed mortality rates are based on estimated deaths for each area during the period 2019–2022, with change between 2023 and 2048 consistent with the mortality assumptions from the National population projections: 2022(base)–2073. Under the median mortality assumption, period life expectancy at birth at the national level is assumed to increase from 80.8 years in 2023 to 84.2 years in 2048 for males (an increase of 3.4 years of life), and from 84.1 years to 87.3 years for females (an increase of 3.2 years). The assumed medium life expectancy at birth remains lowest in the Wairoa district throughout the projection period, increasing from 76.0 years in 2019–2023 to 79.3 years in 2044–2048 for males (an increase of 3.3 years), and from 79.6 years to 82.7 years for females (an increase of 3.1 years). The assumed medium life expectancy is highest in both Queenstown-Lakes and Selwyn districts throughout the projection period, increasing from 84.7 years in 2019–2023 to 87.7 for males in Queenstown-Lakes, and 87.6 years for males in Selwyn in 2044–2048. This is an increase of 3.0 years and 2.9 years respectively. For females in both Queenstown-Lakes and Selwyn districts, assumed life expectancy at birth increases from 88.0 years to 90.7 years over the same periods. This is an increase of 2.7 years of life for females over the projection period. Migration Migration at the subnational level has both an internal (to/from other areas of New Zealand) and an external (to/from overseas) component, although these separate components are difficult to quantify. The assumed net migration (both external and internal) for each area is based on considering observed net migration during each intercensal period from 1996 to 2018, estimated annual net migration from 2019 and 2022, the capacity of the area for further growth (for areas with net inflow), whether historical outflows can be sustained (for areas with net outflow), the desirability of the area to new migrants, and information available from and about local authorities relating to current and future developments that may affect population change. Under the medium migration assumption, annual net migration at the national level is consistent with the national median assumption of -2,000 in 2023, 7,000 in 2024, 16,000 in 2025, and 25,000 in 2026 and beyond. However, the median assumption is not an assumed migration level expected to happen every year, but an overall average that could vary year to year based on the median of the migration simulations that vary around that median. The low and high net migration assumptions are chosen to represent plausible alternative migration scenarios for each area, so are not constrained to any national-level projections. The age-sex patterns of net migration for each area are based on observed intercensal net migration patterns during 1996–2018, see Subnational population estimates: At 30 June 2022 (provisional) (since 2018), and the latest migration assumptions from the National population projections: 2022(base)–2073. en-NZ