# National Population Estimates: September 2010 quarter

## Commentary

### Background

This release contains estimates of the resident population of New Zealand at 30 September 2010. Tables are included at the end of this release with estimated resident population and population change, estimated resident population by broad age group and sex, and by five-year age group and sex. Estimates by single-year of age are available via Infoshare on the Statistics New Zealand website (**demography age estimates** in the '**Population**' category).

Population estimates give the best available measure of the size and age-sex structure of the population usually living in an area. Estimates are based on the latest census data and on births, deaths, and migration since the census. National population estimates are published quarterly and subnational population estimates are published annually.

The estimates in this release are provisional. They incorporate provisional estimates of the number of births and deaths that occurred in the September 2010 quarter. Final estimates will be released in February 2011. In addition, population estimates after 30 June 2006 will be revised following results from the 2011 Census of Population and Dwellings.

In this release, a special topic analyses the mean, median, and modal ages of the population between 1970 and 2010. Recent releases have included special topics on the components of population change, 1970–2010, median age of the population aged 65 years and over, trends in the number of children (aged 0–14 years), 1969–2009, trends in the working-age population, 1979–2009, and an international comparison: percentage of population aged 65+.

### Estimated resident population

The estimated resident population of New Zealand was 4,380,700 at 30 September 2010, comprising 2,151,300 males and 2,229,400 females. At 30 September 2010, there were 96 males for every 100 females. The estimated resident population for the mean year ended 30 September 2010 was 4,358,200.

### Annual population change

In the September 2010 year, the estimated resident population grew by 49,400 (1.1 percent), compared with 51,500 (1.2 percent) in the previous September year. The population growth in the September 2010 year was less than the average annual increase of 51,600 (1.3 percent) recorded during the 10-year period to September 2010.

The population growth for the September 2010 year resulted from a natural increase (excess of births over deaths) of 35,400 and a net permanent and long-term (PLT) migration gain of 13,900. The level of net PLT migration has decreased by more than 3,000 since the previous September year, largely due to a decline in PLT arrivals.

Historically, natural increase has been the dominant component of population growth. Over the last 40 years, natural increase has accounted for around 80 percent of New Zealand's total population growth. During the September 2010 year, natural increase accounted for over 70 percent of population growth.

### Quarterly population change

During the September 2010 quarter, New Zealand's estimated resident population grew by 12,900 (0.3 percent). This growth resulted from a natural increase of 8,100 and a net PLT migration gain of 4,800. In the September 2009 quarter natural increase was comparable (8,100), while net migration was higher (7,400), resulting in quarterly population growth of 15,500 (0.4 percent).

### Median age

New Zealand has an ageing population because of a shift to sustained low fertility and low mortality rates. This shift is also observed across other countries in the Organisation for Economic Co-operation and Development (OECD). At 30 September 2010, half of New Zealand's population was over 36.7 years, compared with a median age of 34.4 years a decade earlier. The median age for males is now 35.5 years, while for females it is 37.7 years. The lower median age for males largely reflects their lower life expectancy of 78.4 years, compared with 82.4 years for females (New Zealand abridged life table, 2007–09). Latest national population projections (2009 base–2061 update) indicate that the median age of the New Zealand population will be 43.5 years in 2061 (series 5).

### Mean, median, and modal age of the population, 1970–2010

Mean, median, and mode can measure the central tendency of the age distribution of the population; the mean age is the mathematical average of all the ages, the median age is the age at which half the population is older and half is younger, and the modal age is the most common age – the age with the largest population.

The mean and median ages of both males and females have steadily increased since 1970, reflecting the general ageing of the population. The mean and median ages are converging as the number of older people relative to younger people increases. In 1970 the mean ages for males and females (29.7 and 31.3, respectively) were five years higher than the median ages (24.8 and 26.4, respectively). This gap has closed over time; in September 2010 the mean and median ages were 36.5 and 35.5 for males, and 38.1 and 37.7 for females, respectively.

The modal age shows a similar pattern for males and females from 1970 to 1989; following a cohort born in the early 1960s through to age 18 in 1980, then a younger cohort through to age 18 in 1989. At this point the patterns for males and females diverge; the female modal age was 28 in 1990 and continues to follow that cohort through to September 2010, with the exception of 1991, where the modal age was 20. The volatility in the modal age is due to the small differences between population size at each age. The male modal age continues to follow the same cohort up to age 19 in 1990, then drops back to age 0 and follows that cohort until age 20 in 2010. The male modal age pattern reflects the high out-migration levels in the younger male working-age population.

### Changes in age composition

The age composition of New Zealand's population has changed over the past decade. In the 10 years ended 30 September 2010, the number of children (aged 0–14 years) grew to 894,800, an average annual increase of 1,600 (0.2 percent). For the year ended 30 September 2010, the increase of 2,700 (0.3 percent) in the number of children was 50 percent greater than the average annual increase for the decade. At 30 September 2010, children accounted for 20 percent of the New Zealand population, down from 23 percent at 30 September 2000.

At 30 September 2010, the population aged 15–39 years remained the largest population group, accounting for 34 percent of the total population, down from 36 percent a decade earlier. This age group reached 1,499,900, up by 10,400 (0.7 percent) compared with the September 2009 figure. In the 10 years ended September 2010, the average annual increase for this age group was 10,200 (0.7 percent).

The population aged 40–64 also remained a large proportion of the population, increasing from 29 percent to 32 percent in the decade ended 30 September 2010. This age group increased by 18,800 (1.3 percent) in the year ended 30 September 2010, to reach 1,412,300. The increase was below the average annual increase of 27,900 (2.2 percent) for the 10 years ended September 2010.

The proportion of the population aged 65–79 years was 9.6 percent at 30 September 2010, up from 9.0 percent in 2000. During the September 2010 year, the population aged 65–79 years increased by 3.0 percent (12,500) to reach 421,800. In the 10 years ended September 2010, this age group grew at an average annual rate of 2.0 percent (7,600).

In the 10 years ended September 2010, there was also an increase in the proportion of the population aged 80 years and over (80+), from 2.8 percent to 3.5 percent. The 80+ population reached 151,800 at 30 September 2010, an average annual increase of 3.4 percent (4,300) over the decade. The size and growth rate of this age group varied significantly by sex. The average annual growth rate for males for the decade was 4.9 percent, compared with 2.5 percent for females. In the year ended 30 September 2010, the male population in the 80+ age group increased by 4.7 percent (2,600) to reach 59,300, while the female population increased by 2.7 percent (2,400) to 92,500.

### Population clock

Statistics NZ's online population clock gives a real-time approximation of the estimated resident population of New Zealand. The population clock uses the latest quarterly estimated resident population, and estimates for the expected number of births, deaths, and net migration during the following quarter. The settings for each component (births, deaths, and net migration) are derived by converting the quarterly estimated totals into a 'per minute' figure, making allowance for the number of days per quarter. The population clock can be viewed on the Statistics NZ website: www.stats.govt.nz.

### Different population measures

Users of population statistics need to be aware that there are three main population measures produced by Statistics NZ: the census night population count, the census usually resident population count, and the estimated resident population. The population counts published from the census are not comparable with the estimated resident population. The estimated resident population includes adjustments for net census undercount and for New Zealand residents temporarily overseas on census night. For more information see the 'Technical notes' section of this release.

For technical information contact:

Esther Hogenhout or Lucy Abrahams

Christchurch 03 964 8700 **Email**: demography@stats.govt.nz

**Next release... **

*National Population Estimates: December 2010 quarter *will be released on 14 February 2011.