Migration is a persistently hot topic and tends to dominate discussion around trends in population growth, taking the limelight away from the other components of population change – births (fertility) and deaths (mortality).

However, New Zealand’s fertility rate recently reached a record low, so this article explores trends in fertility and what’s driving it. We also explore the effect of growing ethnic diversity and barriers to ‘have more babies’.

New Zealand’s fertility rate has fallen substantially since the baby boom of the 1950s and 1960s, with the crude birth rate (births per 1,000 population) down from 27 at the peak in 1962 to 15 in 2009 (see Chart 1). The crude birth rate has fallen consistently since 2009, down to a record low of 11 births per 1,000 population in the year to March 2024.

Chart 1 also shows the mini baby boom of the late 1980s and early 1990s as the children of the baby boomers had children themselves. These children are an echo of the baby boomers – echo boomers, if you like.

A more nuanced measure is the total fertility rate – the average number of children that a woman of childbearing age (15-44 years) can expect to have through their reproductive years. A total fertility rate of 2.1 is regarded as the minimum replacement level for a developed country – 2.0 to replace the parents, and 0.1 to offset mortality before childbearing age. Chart 2 shows that New Zealand’s total fertility rate was last above 2.1 in 2011, falling sharply since to a record low of just 1.52 in the year to March 2024. Putting this rate into perspective, it is well below Stats NZ’s median projection for total fertility of 1.65 for the 2024 to 2028 period. In other words, we expected fertility to ease, but it’s worse than expected.

The number of births fell 4.1% in the year to March 2024, at the same time as our population grew 2.5%. It’s particularly striking that we are experiencing a record low for fertility at the same time as a record high for population growth – perfectly illustrating our shift from natural increase-led population growth to migration-led population growth.

Falls in the total fertility rate are compounded by falls in the relative size of our childbearing age population. The share of the population that is female and of childbearing age fell from 23.8% in 1991, to 20.0% in 2020, to 19.8% in 2022, followed by a minor bounce back up to 20.2% in 2024. However, the recent minor bounce back is a net figure, masking considerable inbound and outbound migration. In the year to March 2024, 38,700 females of childbearing age departed, and 75,000 arrived. If we assume that recent migrant arrivals take time to settle before considering starting a family in New Zealand, then excluding those that have arrived in the past year, the childbearing age population accounts for 18.8% of the overall population in 2024.

Looking out over the long term, the childbearing age population is barely expected to grow, with projected total growth of 3% by 2053, compared to 19% growth in the total population.

At the same time as our fertility rate has changed, when we have children has changed substantially too. Chart 3 shows that in 1981, 68% of children were born to mothers in their twenties, and just 20% born to mothers in their thirties. By 2001, a roughly equal number of children were born to mothers in their twenties and thirties. In 2024, 38% of children were born to mothers in their twenties, and the majority (55%) were born to mothers in their thirties.

Since 2018, more children are born to mothers aged 40 years or older, than mothers under the age of 20. The number of births to mothers under the age of 20 has plummeted from over 5,000 in 2009 to less than 2,000 since 2020. The number of births to mothers aged 40 years or older has held steady at around 2,500 since 2009.

Up to now, we’ve focused on overall births and fertility, but there are significant differences in fertility across ethnic groups. Chart 4 shows that as of 2018, the total fertility rate for Māori (2.14) and Pacific Peoples (2.19) was only just above the replacement rate of 2.1. The total fertility rate for European or Other (1.75) and Asian (1.40) was substantially below replacement rate. This differential means that regions with stronger Māori and Pacific Peoples populations tend to have a higher fertility rate overall, and therefore higher births and natural population increase.

Māori and Pacific Peoples are projected to account for an increasing share of the population, with their relatively strong fertility rates being a key factor shoring up overall fertility rates. Net migration gain is also a key factor for the growing share of the population identifying with Pacific Peoples and Asian ethnicities. However, despite higher overall rates relative to other ethnic groups, Māori and Pacific Peoples fertility rates have still declined considerably in the past 20 years, and in time could dip below replacement rate too.

Population projections, and the projected fertility rates that underpin them, already assume significant growth in non-European ethnicities, and the positive effect on overall fertility rates. These factors already being incorporated into projections mean that there is no unexpected upside for fertility or population growth from growing ethnicity diversity – unless we become substantially more diverse than expected, by receiving substantially higher net migration than expected.

Fertility has a significant impact on our population growth, especially for regions which don’t receive great volumes of net migration. So, it’s natural to look to fertility and think about what we can do to influence (specifically, increase) fertility rates. Indeed, then-Leader of the Opposition (now Prime Minister) Christopher Luxon jokingly suggested last year that it would be helpful if New Zealanders “have more babies”.

Of course, the answer is more subtle than that, and it is illustrative to consider the barriers to having children first.

Firstly, the childbearing age population is increasingly engaged in the labour force. The share of females aged 15-44 that are employed has risen from 64% in 1987 to 74% in 2024 (see Chart 5). Focusing on the now-prime childbearing ages of 30-39 years, the share of females that are employed has risen even faster, from 65% to 80%. The employment rate for the total population aged 30-39 years has risen from 79% to 86% over the same period.

Growing participation of females in employment is, of course, a positive trend. However, without a corresponding easing in the male employment rate in these age groups, higher female participation indicates an increased proportion of couples with both partners working. Having both partners working likely acts as a barrier for having children, especially if they can’t manage to find flexible working arrangements, coupled with a period of forgone or lower earnings after childbirth.

As to why employment rates have risen for both males and females – housing affordability has something to do with it.

The increasing unaffordability of housing in New Zealand means that having multiple earners in a household is increasingly a necessity. In 1989, the average house price in New Zealand amounted to 4.2 times the average earnings for a full-time equivalent employee. In 2024 that ratio was 11.1 – a rate at which it is practically impossible to buy an average house with the income from one average job (see Chart 6).

Looking at household incomes, which take into account households with multiple earners, the house price to income ratio has blown out from 3.9 in 2000 to 6.8 in 2024. When having both parents working is a necessity to meet housing costs, it also quite clearly presents a barrier to having children.

Rather than simply calling for people to have more children, perhaps we should start by addressing the barriers to having children. Greater availability of flexible working opportunities and better housing affordability would all likely make a difference – but are no small feat.