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Over the past decade, New Zealand's fertility rate has plummeted.
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It now sits around 1.6 children per woman, on average - a decrease of around 20 percent in the last decade, and well below the replacement rate of 2.1 - the average number of children each woman needs to have for a population to replace itself in the long term.
In many ways, this is the consequence of undeniably positive social change.
Contraceptives are more readily available. Women have more choice when it comes to education and work. Teen pregnancies have dropped off a cliff.
But there are also pitfalls.
With an ageing population, who will look after us? Who will pay taxes and bolster up the workforce? How much do we want to rely on a steady flow of migrants in order to keep society ticking over?
On today's episode of The Detail, Emile Donovan sits down with Massey University distinguished professor Paul Spoonley to dig into the data about what New Zealand might look like in a couple of decades - and what that can tell us about how to prepare.
New Zealand is by no means alone in this situation.
In Japan, for example, where about 126 million people live now, fertility rates have been dropping since the 1970s.
It's estimated Japan’s population will drop to around 86 million by 2060.
However, the speed of New Zealand's decline is notable, Spoonley says.
As recently as 2010, the rate here was about 2.17 births per woman: meaning fertility rates have declined by a quarter in a single decade.
To put that into perspective, in 1960 the average woman in New Zealand had four children.
Spoonley says the reasons for this are, in fact, reasonably obvious: increased access for women to higher education, and participation in the job market.
There are demographic shifts, too; women are having children much later in life.
Last year, more women over the age of 40 gave birth than did those under the age of 20.
"If you go back 20 or 30 years, the number of births to teenage mothers in New Zealand was very high - 69 per 1,000 women aged under 20.
"Now it's 12. So we've had that very significant shift in terms of teenage sexual behaviour ... but alongside that we have women who are choosing to have children much later in life - typically in their 30s, and increasingly in their 40s."
In addition, Spoonley says, there have been social changes. These days it's perfectly socially acceptable to have just one child, or not to have children at all, whereas in the past this might have raised an eyebrow.
Younger generations are also much more mindful of the impact an increasing population has on the environment.
But there are knock-on effects.
"When you think about that birth rate of 1.61 in 2020 ... in five years' time, it's going to impact on the number of kids arriving at primary school.
"In 20 years’ time it'll impact upon the number of kids at university, or in the labour market.
"What we're going to see is a contraction of our, for example, working-age population. So where do we get our workers from?
"It's what I call 'who's going to wipe my chin?'
"Who's going to be the elder care worker when I require support?”
Spoonley says in the absence of another baby boom, we should be using our human resources more cleverly.
"What you need to do, if you've got a reduced number of children, is increase the investment - in their health, in their welfare, and in their education.
"And with smaller numbers you can do that."