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National Population Projections: 2009 (base)–2061
Embargoed until 10:45am  –  27 October 2009
Technical notes

Latest projections

This release contains 2009-base projections of the population usually living in New Zealand. The projections supersede the 2006-base series released in October 2007. The new projections cover the period 2010–2061 at one-year intervals. More detailed projection results, including projections for individual years and projections by age and sex, are available from Table Builder on the Statistics NZ website (www.stats.govt.nz). Special projections can also be produced for clients using their own assumptions. For more information and quotes, email demography@stats.govt.nz or phone toll-free 0508 525 525.

Base population

These projections have as a base the estimated resident population (provisional) of New Zealand at 30 June 2009. This population (4.316 million) was derived from the estimated resident population of New Zealand (4.185 million) at 30 June 2006, updated for births, deaths, and net migration between 30 June 2006 and 30 June 2009 (+131,000). The estimated resident population of New Zealand at 30 June 2009 was derived from the census usually resident population count (4.028 million) at 7 March 2006 with adjustments for:

  1. net census undercount (+80,000)
  2. residents temporarily overseas on census night (+64,000)
  3. births, deaths and net migration between census night and 30 June 2006 (+9,000)
  4. reconciliation with demographic estimates at ages 0–4 years (+3,000).

For information about the base population, refer to Information About the Population Estimates on the Statistics New Zealand website (www.stats.govt.nz).

Alternative series

Nine alternative series have been produced using different combinations of fertility, mortality and migration assumptions. At the time of release, projection series 5 is considered the most suitable for assessing future population changes. The other projection series allow users to assess the impact on population size and structure resulting from changes in the assumptions for each of the components of population change. Series 4, 5, and 6 can be used for assessing the effect of the different migration assumptions; series 3, 5, and 7 allow for a comparative mortality analysis; and series 2, 5, and 8 allow for a comparative fertility analysis.

Series 1 and 9 give the lowest and highest projected population, respectively, based on the adopted assumptions. Series 1 uses low fertility, high mortality, and low net migration. Series 9 uses high fertility, low mortality, and high net migration. Five additional series have also been produced to illustrate how the population will change if certain demographic events were to occur:

  1. Very high fertility. The total fertility rate increases from 2.14 births per woman in 2009 to 2.21 in 2011, 2.37 in 2016, 2.46 in 2021, 2.50 in 2026, and then remains constant.
  2. Very low mortality. Life expectancy at birth increases at a similar annual rate as between the 1975–77 and 2005–07 complete period life tables (ie by 0.30 and 0.22 years of life for males and females, respectively) to reach 95.0 years of life for both males and females in 2061.
  3. No migration. No external migration at any age throughout the projection period (ie a 'closed' population).
  4. Cyclic migration. Annual net migration fluctuates between -10,000 and 30,000 over a 10-year cycle, with an average of 10,000.
  5. Very high migration. Annual net migration of 25,000 throughout the projection period.

Method

The cohort component method was used to derive the population projections. By this method, the base population is projected forward by calculating the effects of deaths and migration within each age-sex group according to specified mortality and migration assumptions. New birth cohorts are generated by applying specified fertility assumptions to the female population of childbearing age.

Projection assumptions

Projection assumptions are formulated after analysis of short-term and long-term historical trends, recent trends and patterns observed in other countries, government policy, and any other relevant information.

Fertility

There are three alternative fertility variants – designated low, medium, and high – which assume that fertility rates will vary until the year 2026 when the total fertility rate will reach 1.70, 1.90, and 2.10 births per woman, respectively. After 2026, fertility rates are assumed to stay constant. The total fertility rate in the year ended June 2009 was 2.14 births per woman (based on births by date of registration).

The medium fertility variant assumes fertility rates of women aged under 32 years will decline between 2009 and 2026, but increase for women aged 32 years and over. By comparison, the low fertility variant assumes fertility rates will decrease between 2009 and 2026 at most ages. The high fertility variant assumes that fertility rates of women aged under 32 years will drop between 2009 and 2026, but increase for women aged 32 years and over.

A sex ratio at birth of 105.5 males per 100 females is assumed, based on the historical annual average of the New Zealand population.

Graph 

Mortality

There are three alternative mortality variants – designated low, medium, and high – which assume that mortality rates will continue to drop so that the period life expectancy at birth for males will increase to 88.6, 85.6, and 82.6 years, respectively, by 2061. The corresponding life expectancies for females in 2061 will be 91.2, 88.7, and 86.2 years. The life expectancy at birth in 2005–07, from complete period life tables, was 78.0 years for males and 82.2 years for females.

Mortality rates are assumed to decrease at different rates at different ages. Between 2006 and 2061, male mortality rates are assumed to decrease by an average of 2.1, 1.6, and 1.0 percent per year for the low, medium, and high mortality variants, respectively. By comparison, female mortality rates are assumed to decrease by an average of 2.4, 1.8, and 1.3 percent per year for the low, medium, and high mortality variants, respectively.

For more information about the method, refer to Information About the Demographic Projections on the Statistics New Zealand website (www.stats.govt.nz).

Graph 

Migration

There are three alternative migration variants – designated low, medium, and high – which assume long-run annual net migration of 5,000, 10,000, and 15,000, respectively. The medium migration variant assumes net migration of 25,000 in 2010, 19,000 in 2011, and 14,000 in 2012. The low and high migration variants are 5,000 lower and higher, respectively, than the medium variant for each year. These levels are based on an analysis of immigration permits, residence applications and approvals, overseas student numbers, and arrivals and departures analysed by characteristics such as citizenship, country of last/next permanent residence, and age.

Graph

Consistent with historical and recent trends, the age-sex patterns of net migration assume the main net outflow at ages 22–25 years, mainly due to young New Zealanders embarking on overseas travel and the departure of students from overseas after studying in New Zealand. Net inflows are assumed for most other ages with the highest net inflows at 15–20 and 27–37 years.

Nature of projections

Demographic projections are designed to meet both short-term and long-term planning needs, but are not designed to be exact forecasts or to project specific annual variation. These projections are based on assumptions made about future fertility, mortality, and migration patterns of the population. Although the assumptions are carefully formulated to represent future trends, they are subject to uncertainty. Therefore, the projections should be used as guidelines and an indication of the overall trend, rather than as exact forecasts.

The projections do not take into account non-demographic factors (eg war, catastrophes, major government and business decisions) which may invalidate the projections. Demographic trends are monitored regularly and, when it is necessary, the projections are revised to reflect new trends and to maintain their relevance and usefulness.

For more information about the projections, refer to Information About the Demographic Projections on the Statistics New Zealand website (www.stats.govt.nz).

Definitions

Baby boomer: usually someone born in the years 1946–65, although the definition of the baby boom period varies between sources and between countries.

De facto population concept: a statistical basis for a population in terms of those present in a given area at a given time. The census night population count is a census measure of the de facto population concept, and the estimated de facto population is a demographic measure of the de facto population concept.

Estimated resident population: an estimate of all people who usually live in New Zealand at a given date. It includes all residents present in New Zealand and counted by the census (census usually resident population count), residents who are temporarily overseas (who are not included in the census), and an adjustment for residents missed or counted more than once by the census (net census undercount). Visitors from overseas are excluded.

Life expectancy: the average length of life remaining at a given age. In a period life table, it is the average length of life from a given age, assuming people experience the age-specific mortality rates of a given period from the given age onwards.

Replacement fertility: generally refers to a total fertility rate of 2.1 children per woman, which equates to the average number of children each woman is required to have for a population to replace itself in the long term, without migration. The rate allows for the sex ratio at birth (roughly 105 males born for every 100 females) and for some mortality of females between birth and childbearing.

Resident population concept: a statistical basis for a population in terms of those who usually live in a given area at a given time. The census usually resident population count is a census measure of the resident population concept, and the estimated resident population is a demographic measure of the resident population concept. In terms of vital statistics, the resident population concept refers to events that relate to residents of New Zealand only.

Total fertility rate: the average number of live births that a woman would have during her life if she experienced the age-specific fertility rates of a given period (usually a year).

Copyright

Information obtained from Statistics New Zealand may be freely used, reproduced, or quoted unless otherwise specified. In all cases Statistics New Zealand must be acknowledged as the source.

Liability

While care has been used in processing, analysing and extracting information, Statistics New Zealand gives no warranty that the information supplied is free from error. Statistics New Zealand shall not be liable for any loss suffered through the use, directly or indirectly, of any information, product or service.

Timing

Timed statistical releases are delivered using postal and electronic services provided by third parties. Delivery of these releases may be delayed by circumstances outside the control of Statistics New Zealand. Statistics New Zealand accepts no responsibility for any such delays.

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