John Byrne Murdoch

The fundamental issue here is that when countries have very low fertility rates, you have big problems coming down the track.

Hello.

Thanks for having me.

So one thing to emphasize straight out of the gate here is that birth rates have been declining for decades or even centuries over most of the world.

But during the latter part of the last century and this century, they were actually stabilizing in most high and middle income countries worldwide.

But then what is striking is that over the last 15 years or so, that stabilisation has become a decline, which applies in the US, it applies in the UK.

The one that I think really jumps out to me is that Mexico, significantly poorer than its northern neighbour, the US, Mexico now has a lower birth rate than America.

And that's also true now for Brazil, Tunisia, Sri Lanka.

It's even true for Iran, which is an incredibly different country in terms of both economic development and culture to the countries we usually associate with this.

So demographers talk about this number, the replacement rate, which is when a society sees women having an average of 2.1 children.

That means that without immigration, your population is going to be relatively stable.

And the number of countries that are now below that replacement rate

That is now two thirds of the world's countries.

And in 66 countries, the average number of children each woman gives birth to is now closer to one than two.

Within a small number of cases, the most common number is now zero.

On some level, whether or not to have kids is entirely on decision that women make and as it should be.

But there are so many factors at work here.

Several parts of this could come under the economics tag.

So housing is a big one, right?

And unsurprisingly, if young adults are finding it harder to transition into secure, stable, long-term housing, that can be a barrier to secure, long-term, stable relationships where you might have kids.