Ok, here is the scenario.
I was reading about some breakthroughs in medical tech, mainly around the treatment of heart disease. But a few others.
Lets say in 2030 following a bunch of significant break through discoveries, expectancy for those that can afford it goes from currently ~85 to ~150. Initially only the super rich can afford it, but it doesn’t take long for it to become an order of magnitude cheaper.
By 2050 the original tech (which is mostly out dated), is the same cost as a nice new car ~$50k in today’s money, the cutting edge stuff is still 1000x the cost but has a much more significant effect, think at least another 300 years.
The same pattern holds, by 2070 the the original tech is $500, the 300 year tech is $50k and effective immortality (medical) is now available in the market for $50M.
What would the ramifications be on society?
You are correct, that was a remembered stat, it must have included the emigration. Looking at births-and-deaths shows that the “natural increase” is shrinking considerably though.
I find it super interesting that the number of births has hovered around 60,000 for most of the last 70 years or so while our population has gone from about 2 million to over 5 million in that time.