The shape of our population profile shapes how we grow up, how we think about our future, and our role in society.

This chart explains in broad brush strokes how generations in Australia were impacted by the demographic profile they grew up in.

We have longitudinal data going back to federation (1901) but for today we shall only go back to 1921 to make it an even 100 year perspective when counting backwards from the 2021 census.

To compare the population profiles of Australia at 5.5 million (1921), 13.1 million (1971), and 25.7 million (2021) people looking at absolute and relative numbers is important.

Australia quintupled its population base over the last century.

Growth, growth, and then some more growth. In the period immediately after the Second World War birth rates shot up and population growth was driven by babies. The resulting generation was aptly named Baby Boomers.

As birth rates kept falling, Australia shifted to importing population from overseas. Today Australia truly is a migration nation, and two-thirds of our annual population growth comes from overseas while only one-third is homemade (more babies than deaths).

Just quickly glancing at the chart above you notice that our age profile started taking on a different shape. This trend becomes more obvious once we look at relative population profiles in 1921, 1971, and 2021.

In 1921 and 1971 babies were the most common type of people in Australia. Wherever you looked, young parents and kids could be seen.

With each additional year of age, the number of people shrank. Lots of young folks, fewer middle-aged people, very few old folks. By 2021, the population profile changed its shape significantly.

Only half as many Australians (in relative terms) were babies and toddlers in 2021 than a century earlier. Depending on your neighbourhood, kids can be a relatively rare sight.

In 1921 over 40 per cent of the population was aged under 20. By 2021 that share fell to 24 per cent. In 1979 when Pink Floyd proclaimed, “we don’t need no education” the under 20s still made up 35 per cent of all Australians. Songs like this hit much harder when a youth cohort is big in numbers.

The young people of the 1970s are of course the Baby Boomers who through their strength in numbers have transformed every stage of the lifecycle they ever lived through.

Over time the population in their 20s and 30s started to stand out like a camel’s hump. That’s the impact of migration again. Around 80 per cent of migrants are aged between 18 and 39.

We mostly take in international students (late teens and early twenties) and youngish skilled migrants. We want to grab the skilled migrants as young as possible to ensure we get them on cheap starter wages to begin with and of course want them to be productive worker bees for as long as possible.

The relative prominence of people aged 35 to 44 has not changed much since 1921. They live very different lives now though. In 1921, at 40 you’ve already waved your grown kids goodbye, while in 2021 for many this is just the start of their childrearing years.

Young people today complaining about a housing market stacked against them have little demographic power behind their cries for reform. The 45+ cohort overwhelmingly owns their own homes and are unsympathetic towards reforms they fear will drive down the value of their biggest asset (the family home).

The ageing of the population is obvious in this view too. Only 4 per cent of the population were aged 65+ a century ago. By now the share of the population of retirement age quadrupled and over 17 per cent of us fall into this age group.

The ageing of the Australian population was a foregone conclusion once all the Baby Boomers were born. Demographers knew that the population profile was going to shift dramatically. Cynical souls claim that politicians are only interested in short-term developments but in the 1980s they dreamt up the superannuation scheme as they realised the pension system was going to collapse under the weight of the retiring Baby Boomer cohort.

I remind people and politicians that long-term structural reforms are not only possible but crucial if we want to ensure continued prosperity for all Australians.

The overall economy, businesses large and small, and all levels of government eventually adjust themselves to shifts in our national population profile.

We know that the ageing of Australia is going to continue. The next stage of the lifecycle that Baby Boomers will reshape is retirement.

It will be fun to have a more mobile, richer, and travel hungry cohort of retirees. Things will get serious once Baby Boomers hit 85 (that’s six years away) and need care at scale.

The aged care system will need to be completely overhauled. Here’s hoping we can pull this transformation off too.

Demographer Simon Kuestenmacher is a co-founder of The Demographics Group. His columns, media commentary and public speaking focus on current socio-demographic trends and how these impact Australia. His latest book aims to awaken the love of maps and data in young readers. Follow Simon on Twitter (X), Facebook, LinkedIn for daily data insights in short format.