This one demographic; it’s the potential for population collapse in the People’s Republic of China.  Most of the nations of the world outside Africa face population declines, but none seem as severe as the PRC’s is looking to be.

In 2016, after the one-child policy was abandoned, there were 17.86 million births. This dropped to 17.2 million in 2017 and 15.2 million in 2018—the third-lowest rate since the foundation of the People’s Republic of China in 1949.

That might be an accelerating drop, although three data points don’t make for a strongly measured trend.

There’s this datum, too, from Yi Fuxian, Senior Scientist in the University of Wisconsin-Madison’s Medical School Department of Obstetrics & Gynecology:

In China in 2017, the ratio was six workers in the 20-64 age bracket supporting one senior citizen at least 65 years old. This will decline to 2.0 workers in 2039 and 1.6 in 2050.
“No social security net, no family security, and a pension crisis—this will evolve into a humanitarian catastrophe. As women live six to seven years longer than men on average [and are usually a few years younger than their husbands], they will be the main victims of population control,” said Yi.

And this from George Magnus, an Oxford University China Centre Research Associate:

Measured by the proportion of 65+ and the old age dependency ratio, China will age as much in the next 22 years as most Western economies have done in the last 60-70 years—and at far lower levels of income per head, and with a much less developed social security system[.]

It’s unlikely to get better in time to do anything meaningful: the PRC’s fertility rate, the number of children born per woman, as of 2018 is 1.6—far below the 2.1 rate required just to maintain the population at its current level.

But it’s more than just aging women or aging generally.  This is the size of its labor force in absolute terms, too, with its production capacity. The number of Chinese in the labor force is the economic underpinning of the nation and its ability to keep itself armed—to the degree the Communist Party of China and its People’s Liberation Army deem sufficient—and able to face the enemies perceived by the CPC and the PLA.

That economic underpinning also is critical to the nation’s ability to keep its people, including those actively working, fed and housed.

What will a desperate Xi Jinping or Xi-successor do in the face of this crisis?  We need to be prepared diplomatically, economically, and humanitarianly.  And militarily, since neither Xi nor his successor are likely to accept this crisis without resorting to force and invasions to “capture” workers and baby-makers.