Median Age and Our World’s Oldest Populations
Exploring the median age indicator and visualizing two insightful patterns about aging nations.
Hi and welcome back to a new episode of Data Canvas. Today, I want to share two beautiful data visualizations focusing on one of my favourite indicators, median age.
Median age is one of the simplest yet most powerful metrics to describe global development and demography. It divides a population into two equally large groups, one that is older than X years and one that is younger.
Since different countries belong to different stages of demographic development, median age varies significantly across the globe. In some countries, where birth rates are high, half the population is younger than 18 and in others half is older than 40.
Imagine what it means for a country in world that is built on growth to have a young population preparing to contribute or an old one that soon exits the labour force.
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Median age extremes: Japan vs. Central African Republic
First, I wanted to look at the difference between the highest and lowest median age between all countries. I decided to remove countries with a population below 100,000 since they often have strange demographics that don’t follow a natural trend, such as Vatican City and Monaco who both have abnormally high median ages.
When I compared the two countries with the highest and lowest median ages — Japan and the Central African Republic — I discovered a surprising fact. They had the same median age in 1950.
First, I thought there must be something wrong with the data. In my mind, median ages have been rising constantly, similar to survival rates for newly born. But as I looked closer, I discovered that several African countries have a lower median age today compared to 1950.
The reason is that a high enough birth rate and improved survival rates for children leads to an exponential growth of the younger population. Consequently, young people continuously outnumber adults, which can sometimes lower the median age of a country.
That trend intensifies if a large part of the adult population dies or flees the country, a common consequence of armed conflicts. The Central African Republic doesn’t have the highest birth rates, but it’s been one of the world’s most unstable countries in the past 15 years.
Japan, on the other hand, had just recovered from World War II where it lost between 2.6-3.1 million people, most of them soldiers. So their median age in 1950 was probably abnormally low.
China could have the world’s oldest population by 2100
Another interesting question is if Japan will continue to have the world’s highest median age or if someone else comes along and takes the “crown”.
Looking at predictions for all countries, it turns out that the experts believe China will surpass Japan in the middle of the century and have the oldest median age of any country by 2100, closely followed by South Korea.
China does have an abnormal demographic profile because of the one-child policy. They don’t have one of the oldest populations today because most people born during the years of rapid growth are still relatively young at 40-50 years.
But fast-forward 20 years and a large chunk of China’s working population start thinking about retirement with few youngsters ready to take over the reins.
Interestingly, China’s peak median age is almost 10 years higher than that of Japan. That’s because we expect people to live longer. But in Japan, fewer older people actually get to experience that benefit. Eventually, death rates outpace birth rates, which stalls further increases in the median age.
Thank you
This episode of Data Canvas has more meat on its bones compared to previous posts. We’ve looked at two data visualizations showing the extremes in median age and explored the reasons behind the numbers.
If you made it all the way through — I salute you!
Let me know in the comments if there are questions you’d like me to explore in future articles, or if you have feedback that can help me improve this newsletter.
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