Natural Increase and Decrease

Natural Increase occurs when births exceed deaths; Natural Decrease occurs when deaths exceed births. In 2018, New Zealand's births exceeded deaths by a little over 25,000, and natural increase was the dominant situation across the vast majority of the country (at regional and territorial authority area, town and rural centre level). However, as elsewhere in the more developed countries, low birth rates and population ageing are causing New Zealand's natural increase to trend downwards, and natural decrease to slowly emerge. The current natural increase of around 25,000 is substantially lower than the 43,608 occurring at the peak of New Zealand's Baby Boom (1961), despite today's population being twice its 1961 size.

These maps show projected trends across New Zealand’s 67 territorial authority areas (see also Jackson and Cameron 2017). Statistics New Zealand's medium variant projections (2013-base Update) indicate that while natural increase will remain positive at the national level until around mid-century, natural decrease will slowly become the norm at sub-national level. Between 2001 and 2013, just two territorial authority areas experienced sustained natural decrease. Between both 2013 and 2018, and 2018 and 2023, this situation is projected to extend to just three (4.5 per cent). Between 2023 and 2028 that is projected to increase to 5 territorial authority areas, and between 2028 and 2033, to 15 (22 per cent). Between 2033 and 2038, 30 territorial authority areas (45 per cent) are projected to experience natural decrease, increasing to 39 (58 per cent) between 2038 and 2043. Additionally, several other territorial authority areas will experience zero natural increase.

The high and low projections indicate, respectively, fewer and greater proportions to experience natural decrease, but in each case, there is a progression from relatively few TAs affected, to substantially more, across the projection period.

Adding support to these projections, retrospective research undertaken by Jackson and Brabyn (2017: 26) found that between 1976 and 2013, 47 (17 per cent) of New Zealand’s 275 towns and rural centres experienced natural decrease across more than one five-year period, and 22 experienced it across five or more periods. In 2013, 19 towns (13 per cent) and 20 rural centres (15 per cent) were regularly experiencing natural decrease. These findings reflect those for the counties of both the United States and Europe, and confirm that New Zealand is following its structually older counterparts, although is at an earlier stage. However, as was also found for those counties, the primary cause of sub-national New Zealand's past and present natural decrease has been the migration-led deficit of women in the prime reproductive age groups (15-44 years) and the net migration gain of people of retirement age, rather than very low birth rates per se (the conventional cause of natural decrease at national level). It is such dynamics that cause the two territorial authority areas currently experiencing natural decrease to have New Zealand's structurally oldest populations (as measured by percentage aged 65+ years), as it is for most of those projected to enter natural decrease over the next few decades. Notably, none of the relatively youthful cities, nor any of the local board areas of the Auckland Region (N=21), are projected to experience natural decrease before mid-century.

References and further reading

Cochrane W and I Pool (2017) Māori in New Zealand’s contemporary development. Policy Quarterly Supplement 13: 47-54.

Jackson NO and L Brabyn (2017) ‘The mechanisms of subnational population growth and decline in New Zealand, 1976-2013’ Policy Quarterly Supplement 13: 22-36.

Jackson NO, L Brabyn, D Mare, M 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 and A Kulczycki (eds) Studies in the Sociology of Population. International Perspectives. Springer: 161-194.

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 Update