Every generation before ours grew up in a world with more small children than old people. That was simply the shape of things, true globally throughout recorded history. Then, quietly, without any announcement, it stopped being true.

In 2018 the two lines crossed, and almost nobody felt it happen.

A quick note before going further. I’m not a demographer or an economist, and this is a piece of reading and reflection on the numbers, not advice about how any country or family should respond. The data here describes global patterns, and patterns at that scale don’t tell any individual reader much about their own life.

The 2018 crossover and what the numbers actually show

The claim is easy to state and hard to fully absorb. The UN notes that “in 2018 – for the first time in history – persons aged 65 or older outnumbered children under five years of age globally.”

Not for the first time in a century. The first time ever.

People aged 65 and over are now the world’s fastest-growing age group, rising from 5.5 percent of the world’s people in 1974 to 10.3 percent in 2024. That works out to around 800 million people aged 65 and older, more than the entire population of Latin America and the Caribbean.

Two slow trends arriving at the same moment

This wasn’t one event. It was two long, slow changes finally meeting. On one side, people started living much longer: worldwide, a newborn’s expected lifespan rose from 64.0 years in 1990 to 73.3 in 2024. On the other, people started having far fewer children. The average number of births per woman worldwide fell from 3.31 in 1990 to 2.25 in 2024. Go back to the 1960s and that figure was close to four.

The cause is not in dispute. The UN puts it plainly: “virtually every country” is now seeing its share of older people grow, because people are living longer and having fewer children. What I’d flag is that word, virtually: the aging is close to universal, but it isn’t uniform, and the pace differs sharply from one place to the next.

Nor is it holding still. Li Junhua, the UN Under-Secretary-General for Economic and Social Affairs, said in the 2024 release that “the demographic landscape has evolved greatly in recent years.” He added a detail worth keeping in view: “in some countries, the birth rate is now even lower than previously anticipated,” and some high-fertility regions are seeing faster declines than expected too.

What a world tilted this way looks like

The UN expects the share of people aged 65 and over to roughly double again to 20.7 percent by 2074. By the late 2070s the number of people aged 65 and over is expected to reach 2.2 billion, passing the number of children under 18.

The UN calls the wider shift towards older populations “largely irreversible,” which is a strong phrase, but the numbers behind it are stubborn.

Some places are already living in that future. Japan has the highest share of any country except Monaco, with 29 percent of its people aged 65 or older (Monaco is at 36%).

Everyday life quietly organizes itself around the age balance of a society: who pays into pension systems, who staffs hospitals, whether a town decides to build a school or a care home. Shift the balance and all of those questions move at once.

The question nobody has a clean answer to

This is where the confidence runs out. We know where we are. We don’t agree on what to make of it.

The most common worry is economic, and one version of it comes from Torsten Sløk of Deutsche Bank, who framed it as a question: “the key issue for investors in equities, rates, and credit is if the global economy is able to generate enough productivity growth to offset these demographic trends.” In plainer terms: can the economy get efficient enough to make up for having fewer workers per retiree?

That’s one framing, not a settled verdict. Others aren’t convinced the drag is real. Work by economists Daron Acemoglu and Pascual Restrepo found “there is no such negative relationship in the data” between aging and economic growth, and if anything a slightly positive one. They suggest countries adopt machines and automation faster when workers are scarce. The effect is contested, not obvious.

Closing thoughts

 A pattern that held for the entirety of recorded human history ended in our lifetimes, and most of us never noticed the year it happened. The data can tell us that clearly. It can’t tell us how much to worry, or whether an older world is a poorer one or simply a different one. Those are questions we’re going to answer as we go, mostly by living through them.