I’ve yammered on about demographics a lot on this blog, but for reasons I think are important.  It turns out that we don’t think about demographics much, imagining that the future will be a lot like the past.  But that is not necessarily true.  

First, two recent web pieces point to a study published in The Lancet, about global demographics.  Here are the crucial thoughts, at least the ones that stuck out to me:

By century's end, 183 of 195 countries—barring an influx of immigrants—will have fallen below the replacement threshold needed to maintain population levels, an international team of researchers reported in The Lancet.

More than 20 countries—including Japan, Spain, Italy, Thailand, Portugal, South Korea and Poland—will see their numbers diminish by at least half.

China's will fall nearly that much, from 1.4 billion people today to 730 million in 80 years 

Sub-saharan Africa will then have three billion people, three times what it has now.

The US has advantages related to relative openness to immigration, so it will be not affected as strongly as many others; in fact the study suggests that the dominant powers in 2100 will be the United States, India, Nigeria, and China; China will have a brief moment where it is the most economically powerful state, but it will decline from that apogee, and the US will recover the number one spot.

More than this, the demographics will involve major changes in what governments do:

As fertility falls and life expectancy increases worldwide, the number of children under five is forecast to decline by more than 40 percent, from 681 million in 2017 to 401 million in 2100, the study found.

At the other end of the spectrum, 2.37 billion people—more than a quarter of the global population—will be over 65 years old by then.

Those over 80 will balloon from about 140 million today to 866 million.

I don't imagine that--at least since the agricultural revolution, if ever--the aged have outnumbered the young.  We're moving from a relatively youthful species, to a middle-aged species (that's where we'll be for the next few decades, I think), to an aged species.  One of my friends who is an IR theorist has spoken about a "geriatric peace."   This seems to me important, very important.  And culturally--what will it mean to have more than a quarter of the human population people who are in that way not just older, but perhaps wiser?  What will it mean for our cultural discourse?  And will it make us politically more conservative?  It's hard to imagine it not doing that.

At a wholly different level, I recently came across an essay by Jonathan Vespa, Lauren Medina, and David M. Armstrong, entitled “Demographic Turning Points for the United States: Population Projections for 2020 to 2060” (US Census Bureau, Report P25-1144, revised February 2020).

Here's what they say there: 

The year 2030 marks a demographic turning point for the United States. Beginning that year, all baby boomers will be older than 65. This will expand the size of the older population so that one in every five Americans is projected to be retirement age. Later that decade, by 2034, we project that older adults will outnumber children for the first time in U.S. history. The year 2030 marks another demographic first for the United States. That year, because of population aging, immigration is projected to overtake natural increase (the excess of births over deaths) as the primary driver of population growth for the country. As the population ages, the number of deaths is projected to rise substantially, which will slow the country’s natural growth. As a result, net international migration is projected to overtake natural increase, even as levels of migration are projected to remain relatively flat. These three demographic milestones are expected to make the 2030s a transformative decade for the U.S. population.

Beyond 2030, the U.S. population is projected to grow slowly, age considerably, and become more racially and ethnically diverse.

For more, the March 2020 issue of Finance and Development has a series of small articles reflecting on these challenges.  Check it out.

These are big changes, about whose quantitative shape we can have some confidence.  It behooves us to think hard about them.