11–20 of 176 posts
It took me a few minutes to understand the chart shown here, I think because it has the dependent and independent axes inverted. To look at the number of people of a given age in a given year, you follow the line for that year, go down the left to find the given age, and see where it lines up at the top to get the number of people. The shading between the lines is irrelevant and just serves to confuse: the area under…
The area under a line is the global population, no?
This is a really interesting visual presentation of the data. Some cool observations: 1. The first five curves (1950–1990) are all in 10-year increments, so for instance, 1950's 20-year-old population maps very directly to 1960's 30-year-old population (hence the "rippling" effect produced by those six curves). 2. What's with the sudden pinch in the population of 20-year-olds in 2018? It tapers in very heavily from t…
I'm no expert on this but I would guess the peak of China's one-child policy? Someone more knowledgeable might know more about the history of specific exemptions (city vs rural) and such.
There's also implications for reporting bias, which might explain why the older data doesn't look so peaky.
It is interesting to contrast countries at different points on their development. E.g., in Japan, where the population has already started contracting, vs say, Kenya, where the population is still growing rapidly.
However, these curves should come with error bars that grow as you go farther out. There could be all kinds of black swan events we know nothing about right now. A major antibiotic resistant bug could sweep the world, there could a nuclear war, risks of climate change could be worse than we are projecting. If someone in 1900 had made similar curves, I wonder how they would look to us. On that count, I wonder if there are similar projections from, say, 1950 that we could look at and see how they turned out.
In 1950 he'd have been about 6 years old. If you then look at the 2018 curve for 74 year olds, you can see a fairly large part of his cohort has passed. Looks like more than half actually, if I'm interpreting this right.
If you look at it, he's also on that part of the chart where your annual hurdle rate is rapidly increasing. Nobody's surprised that people in their 80s and 90s pass away.
What's maybe a bit more surprising is for younger people, even though your annual loss is quite low, it's still there and accumulating. If you look at 1980, those of us nearing 40 in 2018 are slightly fewer, but it's noticeable.
I'm also of an age where a few of those have started to hit home. I went to a small high school, maybe 90 people in my year plus the two adjacent years. At least 4 have passed away.
This is a really interesting visual presentation of the data. Some cool observations: 1. The first five curves (1950–1990) are all in 10-year increments, so for instance, 1950's 20-year-old population maps very directly to 1960's 30-year-old population (hence the "rippling" effect produced by those six curves). 2. What's with the sudden pinch in the population of 20-year-olds in 2018? It tapers in very heavily from t…
This is largely due to China's population dynamics.
Here I've made a chart that shows the number of births (and deaths) in China over the last 69 years: https://ourworldindata.org/grapher/births-and-deaths-project... 30 and also 50 years ago China had large cohorts of newborns, these are the 'ripples' you see going through the global population pyramid.
The number of births is always determined by two factors: the number of children per woman in the reproductive age bracket (called the Total Fertility Rate). And the number in the reproductive age bracket.
Here is the Total Fertility Rate for China: https://ourworldindata.org/grapher/children-per-woman-un?tab...
The large cohort born around 50 years ago is the parent generation of the large cohort born 30 years ago.
So the question is what explains the large cohort in the 1960s? That is the cohort born right before the rapid reduction of the Total Fertility Rate (from 6.4 children per woman in 1965 to half of that 15 years later as the chart above shows; this is largely before the introduction of the strict one-child-policy by the way). And it is the cohort born after one of the largest mass deaths in history. The Great Leap Forward Famine from around 1951 to 61 https://ourworldindata.org/famines#great-leap-forward-famine... Around 30 million died and as in all famines the fertility rate declined substantially, to then jump again right after the famine.
Good questions! I should have mentioned them in the post. Let me know if you want to know more.
At this point it is useful to reiterate that global population growth right now is no longer exponential. Not even linear. It is sublinear, and the population expected to be stabilized around 2070, in the vicinity of 9-10B.
The projections from different research teams differ in when they expect the population population to peak. IIASA suggests what you say, the UN expects it later. I looked at the different projections (and what is behind the differences) here https://ourworldindata.org/peak-child
Looks like half a vagina to me.
Its an interesting visualization. Another site that shows this for individual countries is https://www.populationpyramid.net/ It is interesting to contrast countries at different points on their development. E.g., in Japan, where the population has already started contracting, vs say, Kenya, where the population is still growing rapidly. However, these curves should come with error bars that grow as you go farther ou…
Thomas Malthus attempted to describe the future of the world population in 1798 in his book, An Essay on the Principle of Population. He predicted a doubling of the global population every 25 years until a lack of food limited the population through hardship or famine and death. Pierre François Verhulst went on to mathematically model this bounded exponential growth and, in doing so, created the logistic function. The necessary data to create a chart like the one in the article didn't exist then, but Malthus' book did contribute to the passage of the Census Act of 1800, which enabled the first census of England, Scotland and Wales.