While the global population of humans will continue to rise for at least another 40 years, demographic trends in full force today make it clear that a much bigger existential threat lies in global underpopulation.
That worry seems preposterous at first. We've all seen the official graph of expected human population growth. A steady rising curve swells past us now at 6 billion and peaks out about 2050. The tally at the expected peak continues to be downgraded by experts; currently UN demographers predict 9.2 billion at the top. The peak may off by a billion or so, but in broad sweep the chart is correct.
But curiously, the charts never show what happens on the other side of the peak. The second half is so often missing that no one even asks for it any longer. It may be because it is pretty scary news. The untold story of the hidden half of the chart is that it projects a steady downward plunge toward fewer and fewer people on the planet each year—and no agreement on how close to zero it can go. In fact there is much more agreement about the peak, than about how few people there will be on the planet in a 100 years.

From Kevin Kelly over at Edge. Lots of interesting data points throughout, and it raises an interesting question: what is the right economic model for a world of fewer people, more of them older?

A country like Japan, already deep in the throes of grappling this dual whammy of lower birth rates and an aging population, has popular art centered around this issue. Roujin Z, an anime movie from Katsuhiro Ôtomo, the creator of the great Akira, built a sci-fi thriller off of this socioeconomic issue. While I have not seen the movie, it sounds from plot summaries as if it was prescient in prescribing an increase in robot labor as one method of bridging the productivity gap that results from this population contraction and demographic aging.

Sometimes I think I should have kids just so that decades from now I'll have someone to teach me how to use the mind control or gestural interfaces on my set top box that allow me to watch reruns of Breaking Bad on my ancient plasma TV.

UPDATE: The plot of Roujin Z may be coming true: "The [Japanese] health ministry is launching a program to promote the use of nursing care robots to meet expected increases in demand in the face of Japan’s rapidly aging population."