National Population Projections: 2006 (base) - 2061

Latest projections

This release contains 2006-base projections of the population usually living in New Zealand. The projections supersede the 2004-base series released in December 2004. The new projections cover the period 2007–2061 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 New Zealand website. 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 of New Zealand at 30 June 2006. This population (4.185 million) 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 (7 March 2006) 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 1.99 births per woman in 2006 to 2.27 in 2011, 2.39 in 2016, 2.47 in 2021, 2.50 in 2026, and then remains constant.
2. Very low mortality. Life expectancy at birth increases at a similar rate as in the 1975–1977 to 2005–2007 period, by 0.31 and 0.23 years of life per year for males and females, respectively, to reach 95 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 base total fertility rate in 2006 was 1.99 births per woman (based on estimated births by date of occurrence).

The medium fertility variant assumes fertility rates of women aged under 32 years will decline between 2006 and 2026, while rates for women aged 32 years and over will increase. By comparison, the low fertility variant assumes fertility rates will decrease between 2006 and 2026 for most ages. The high fertility variant assumes that fertility rates will drop between 2006 and 2026 for women aged under 31 years and increase for women aged 31 years and over.

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

Mortality

There are three alternative mortality variants – designated low, medium and high – which assume that mortality rates will continue to drop so that life expectancy at birth will increase to 87.0, 84.5 and 82.0 years for males, respectively, by 2061. The corresponding life expectancies for females in 2061 will be 90.0, 88.0 and 86.0 years. The base life expectancy at birth in 2005–2007 was 78.2 years for males and 82.2 years for females.

Mortality rates are assumed to decrease at the same rate at all ages. Between 2006 and 2061, male mortality rates are assumed to decrease by about 55, 44 and 29 percent for the low, medium and high mortality variants, respectively. By comparison, female mortality rates are assumed to decrease by about 53, 44 and 31 percent for the low, medium and high mortality variants, respectively.

Migration

There are three alternative migration variants – designated low, medium and high – which assume long-run annual net migration levels of 5,000, 10,000 and 15,000, respectively. Short-run migration levels converging to the long-run levels are assumed for 2007–2009. These short-run 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.

Consistent with historical and recent trends, the age-sex patterns of net migration assume the main net outflow at ages 21–25 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 15–19 and 27–38 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

A baby boomer is usually someone born in the years 1946–1965, although the definition of the baby boom period varies between sources and between countries.

The de facto population concept is 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.

The estimated resident population of New Zealand is 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(ex) is the average length of life remaining at a given age. As derived from a period life table, it assumes that a person experiences the age-specific mortality rates of a given period from the given age onwards. It represents the average longevity of the whole population and does not necessarily reflect the longevity of an individual.

 Replacement fertilitygenerally 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.

The resident population concept is 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.

The total fertility rate is 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).

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