## Projected Percentage Share by Age

These maps show the percentage of each Territorial Authority Area’s (TA) population by broad age group and decade to 2043, according to Statistics New Zealand’s High, Medium and Low Variant assumptions (Statistics New Zealand 2017, 2013(base)–2043 Update, see below). For each age group, white denotes the lowest percentages, and deep red, the highest percentages, with varying shades of pink to red denoting proportions in between.

Maps are given for the following age groups: 0-14, 15-24, 25-44, 45-54, 55-64, 65-74, 65+ and 75+ years, in each case as a percentage of the projected total population of each TA. Maps also given for four key functional age groups: the ‘prime’ working age population (20-69 years), the ‘Labour Market Entry: Exit’ Ratio (the ratio of all people aged 20-29 years to those aged 60-69 years), the ‘Senior: Child Ratio’ (65+ years: 0-14 years), and the ratio of Older to Younger Seniors (75+ years: 65-74 years). Each ratio depicts the number of people in the first age group, per person in the second age group. In general,

- the Labour Market Entry: Exit Ratio falls as the proportion aged 20-29 years declines relative to the increase in the proportion at 60-69 years,
- the Senior to Child Ratio increases as the proportion at older ages increases, relative to the decline in the proportion at younger ages, and
- the Older to Younger Seniors Ratio increases as the proportion at the oldest-old ages increases, relative to the proportion at the youngest-old ages.

The indices illustrate the general progression of structural ageing (the general shift from lower to higher proportions at older ages and from higher to lower proportions at younger ages): at the older ages, the colours deepen over time, while at younger ages they lighten, but in each case do so differently for each TA. However, the generally progressive nature of the trends can also be confusing to interpret, as they are not strictly linear. The differences by variant also require some thinking about. For example, under the high variant assumptions there are lower proportions at older ages (and slower structural ageing), reflecting the greater impact of higher birth rates and higher migration at younger ages, while under the low variant assumptions, proportions at older ages are greater (and structural ageing is accelerated), reflecting the opposite (lower birth rates and migration at the younger ages).

While the raw data underlying these maps have been drawn from Statistics New Zealand, any calculation and interpretation errors are those of the author. It should also be noted that different percentage width bands have been purposefully used to better illustrate variation where overall percentages are larger (for example, at 65+ years) or smaller (for example, at 65-74 years).

The high, medium and low assumptions regarding the total fertility rate (TFR), life expectancy at birth (by sex), and net migration for each TA are available from:http://nzdotstat.stats.govt.nz/wbos/Index.aspx?_ga=2.139904694.464866798.1555814963-487003909.1502250985

### References and further reading

Jackson NO. (2016) Irresistible forces: facing up to demographics change, in P Spoonley (Ed.) Rebooting the Regions. *Why low or zero growth needn’t mean the end of prosperity*. Massey University Press: 49-77.

Jackson NO, L Brabyn, D Maré, MP Cameron and I Pool (2019) From ageing-driven growth towards the ending of growth. Subnational population trends in New Zealand, in J Anson, W Bartl, A Kulczycki (Eds.) *Studies in the Sociology of Population*. International Perspectives. Switzerland: Springer Nature: 161-193. https://doi.org/10.1007/978-3-319-94869-0

Jackson NO and MP Cameron (2017) ‘The unavoidable nature of population ageing and the ageing-driven end of growth - an update for New Zealand’ Population Ageing: 1-26. DOI: 10.1007/s12062-017-9180-8.

Johnson KM, LM Field and DL Poston Jnr (2015) 'More Deaths than Births: Subnational Natural Decrease in Europe and the United States'. *Population and Development Review* 41(4): 651–680.

Statistics New Zealand (2017) Subnational population projections, characteristics, 2013(base) -2043.