Australians are having fewer babies, so many fewer that without international migration our population would be on track to decline in just over a decade.

In most circumstances, the number of babies per woman that a population needs to sustain itself – the so-called total fertility rate – is 2.1.

Australia’s total fertility rate dipped below 2.1 in the late 1970s, moved back up towards it in the late 2000s (assisted in part by an improving economy, better access to childcare and the introduction of the Commonwealth Baby Bonus), and then plunged again, hitting a low of 1.59 during the first year of COVID.

The latest population projections from the Australian Bureau of Statistics assume the rate remains near its present 1.6% for the next 50 years.

An alternative, lower, set of assumptions has the rate falling to 1.45 over the next five years and staying there.

A higher set of assumptions has it rebounding to 1.75 and staying there.

A comprehensive study of global fertility trends published in March in the medical journal The Lancet has Australia’s central case at 1.45, followed by a fall to 1.33 by the end of the century.

Significantly, none of these assumptions envisages a return to replacement rate.

The bureau’s central projection has Australia’s population turning down from 2037 in the absence of a boost from migration.

It’s easy to make guesses about reasons.

Reliable contraception has been widely available for 50 years.

Rents, mortgages and the other costs facing Australians of child-bearing age appear to be climbing.

It’s still difficult to have a career if you have a child, and data show women still carry the substantive burden of unpaid work around the home.

The US fertility rate has fallen much in line with Australia’s.

Reporting on research into the reasons, Forbes Magazine succinctly said a broken economy had “screwed over” Americans considering having children.

More diplomatically, it said Americans saw parenthood as “harder to manage” than they might have in the past.

Half the world is unable to replace itself

But this trend is widespread.

The Lancet study finds more than half of the world’s countries have a fertility rate below replacement level.

China, which is important for the global fertility rate because it makes up such a large share of the world’s population, had a fertility rate as high as 7.5 in the early 1960s.

It fell to 2.5 before the start of China’s one-child policy in the early 1990s and then slid further from 1.8 to 1 after the policy was abandoned in 2016.

South Korea’s fertility rate has dived further, to the world’s lowest: 0.72.

The fertility rate in India, which is now more populous than China, has also fallen below replacement level.

Most of the 94 nations that continue to have above-replacement fertility rates are in North Africa, the Middle East and Sub-Saharan Africa. Some, including Samoa and Papua New Guinea, are in the Pacific.

Most of Asia, Europe and Oceania are already below the replacement rate.

A changing world order

The largest high-fertility African nation, Nigeria, is expected to overtake China to become the world’s second-most-populous nation by the end of the century.

But even Nigeria’s fertility rate will sink.

The Lancet projections have it sliding from 4.7 to 1.87 by the end of the century.

The differences mean the world’s population growth will increasingly take place in countries that are among the most vulnerable to environmental and economic hardship.

Already economically disadvantaged, these nations will need to provide jobs, housing, healthcare and services for rapidly growing populations at a time when the rest of the world does not.

On the other hand, those nations will be blessed with young people.

They will be an increasingly valuable resource as other nations face the challenges of an ageing population and declining workforce.

An older world, then a smaller world

Global fertility halved between 1950 and 2021, shrinking from 4.84 to 2.23.

The latest projections have it sinking below the replacement rate to somewhere between 1.59 and 2.08 by 2050, and then to between 1.25 and 1.96 by 2100.

The world has already seen peak births and peak primary-school-aged children.

In 2016, the world welcomed about 142 million live babies, and since then the number born each year has fallen.

By 2021, it was about 129 million.

The global school-age population aged 6 to 11 years peaked at around 820 million in 2023.

The United Nations expects the world’s population to peak at 10.6 billion in 2086, after which it will begin to fall.

Another forecast, produced as part of the impressive Global Burden of Disease study, has the peak occurring two decades earlier in 2064, with the world’s population peaking at 9.73 billion.

Fewer babies are a sign of success

In many ways, a smaller world is to be welcomed.

The concern common in the 1960s and 1970s that the world’s population was growing faster and faster and the world would soon be unable to feed itself has turned out to be misplaced.

Aside from occasional blips (China’s birth rate in the Year of the Dragon) the fertility trend in just about every nation on Earth is downwards.

The world’s population hasn’t been growing rapidly for long.

Before 1700 it grew by only about 0.4% per year.

By 2100 it will have stabilised and started to fall, limiting the period of unusually rapid growth to four centuries.

In an important way, lower birth rates can be seen as a sign of success.

The richer a society becomes and the more it is able to look after its seniors, the less important it becomes for each couple to have children to care for them in old age.

This is a long-established theory with a name: the demographic transition.

For Australia, even with forecast immigration, lower fertility will mean changes.

The government’s 2023 Intergenerational Report says that whereas there are now 3.7 Australians of traditional working age for each Australian aged 65 and over, by 2063 there will only be 2.6.

It will mean those 2.6 people will have to work smarter, perhaps with greater assistance from artificial intelligence.

Unless they decide to have more babies, which history suggests they won’t.

Guest author is Amanda Davies, Professor and Head of School of Social Sciences, The University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article here.