In 2004, the United Nations put its futurist hat on.
In a report simply titled “World Population to 2300,” the UN’s Department of Economic and Social Affairs released for the first time its predictions about the state of the world over the next 300 years.
This was a major undertaking, to say the least.
Imagine people in 1700 making predictions about the year 2000. Even predictions from 1950 were dead wrong.
Our modelling tools have gotten slightly more sophisticated since the 18th century, however, and given the predictions made for 2300 — a population of 9 billion and people regularly living to 100 — the projections and the UN demographers’ assumptions seem reasonable enough.
On the low end, the UN estimates the year 2300 will see only 2.3 billion people walking the Earth, fewer than we saw in 1940.
On the high end, it predicts 36 billion -- five times the current size.
But tucked in the middle is a number it forecasts will hold steady from approximately 2050 onward: 9 billion.
Fertility rate plays the largest role in deciding which of those three predictions will eventually become the most accurate. Africa, with its sky-high fertility rate, will lead the charge.
Today, the continent makes up just 16% of the world population. By 2100, that slice of the pie is expected to grow to more than 50%.
In the middle of the 20th century, the world saw a population explosion. The US had its Baby Boom, as did China and India. But then as urbanisation and industrialisation continued around the world, and countries like China implemented strict population control policies, people stopped having so many kids.
Today, we are still having approximately 2.5 kids per woman (statistics are fun), so the population keeps growing. However, the rate is falling, which means population growth will level off or even drop if it stays below replacement fertility (the number of kids people need to have to keep the population stable).
In its 2300 report, the UN estimates the rate will not keep falling. It will flatline around replacement fertility sometime in the 2130s.
'That fertility first declines below replacement and then recovers to replacement level, and that population growth follows, with turning points about half a century later' is a general pattern among countries across all regions in the long-range projections, the report explains.
In just about every region between 1950 and 2000, humanity as a whole got older -- except in Africa.
For decades, the continent has seen high HIV/AIDS-related mortality rates and even higher fertility rates. As more babies enter the world, the median age goes down. The UN predicts this trend will eventually end by 2100, however, as medicine keeps that big population of babies alive into adulthood.
Over the next couple centuries, most countries will see their median ages pull closer together.
'By 2200, the list of oldest countries is virtually identical to the list of countries with the highest life expectancies,' the report states. 'Through 2300, there is little further change in the list. By 2300, the Japanese population 65 years and older will be only a slightly larger proportion of the population than in 2050.'
People are living longer than ever. And even by 2300, the UN expects the world will keep living longer, without any plateau effect.
Grouping developed and developing regions together, the UN estimates that women will live to 97 and men to 95 years old. In the developed world, those estimates rise to 99 and 102, respectively.
Extending people's life spans is the surest sign modern medicine is working.
Babies survive childbirth, kids get vaccinated, adults get quick and effective treatment for disease, and old-age care delays death in a peaceful manner.
Of course, there will always be people who reject mortality entirely and strive to live forever.
Broken down by sex, the UN predicts most men -- despite living shorter lives, on average, than females -- will reach their 95th birthdays, if not the 100th.
Even in sub-Saharan African countries like Nigeria, the UN expects the threat of HIV/AIDS to be a relic of the past, making longevity more accessible to people in developing nations.
With this rise in elderly populations will come a new living arrangement for many families.
'This, given our current patterns of old age care and the already visible trends in public resources for such care, implies more multigenerational households,' Alaka Malwade Basu, sociology researcher at Cornell University, wrote in the report.
By 2300, many more women will live to see 100. In Japan, the life expectancy will rise to 108 years. In the US it will rise to 102.
'If there is one stark conclusion in the 2300 population projections, it is the major shift in age distributions worldwide by that time,' Basu wrote. 'In particular, I would speculate that emotional bonds between generations once removed (grandchildren and grandparents) will change drastically by 2300.'
Western countries will likely come to adopt similar attitudes to those of eastern ones, like Japan and China, where seniors are looked upon with great reverence.
As Basu explains, this could result in a reversal of the 'inter-generational flow of emotional resources.'
A world with 9 billion people is a denser world than the one we currently inhabit. But it's certainly doable, and not all regions will be affected equally by 2300.
The UN predicts many nations will become denser with time, such as India and Nigeria. Others, like China and US, aren't likely to see drastic shifts.
Countries that live more densely will likely need to come up with creative solutions to avoid over-crowding. Even today, as vertical living and farming are still in their infancies, certain places are learning how to grow up instead of out.
It's a skill many will learn as the centuries pass.
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