I've been reading Peter Zeihan's take on this — his focus is on Geopolitics (the intersection of demography, geography and technology).

The issue is that for many/most countries, the demography is upside-down (not enough young people for a tax base to support the elder generation). It's particularly bad for China, Russia, and Japan. It's suboptimal in the US, but the Boomer generation did have kids — making it a shorter-term problem than elsewhere.

It's a spectacularly interesting area. His 2014 'Accidental Superpower' has about the best intro to Geopolitics out there. If you've been reading Stratfor for a while, you've probably read at least one of his analyses. He's out on his own now, figuring out what's going to happen and presenting that to investors and military brass - snippets of those make their way to youtube. Worth a watch.

That said, I think he's got most things right - medium terrifying for the Americas, much worse elsewhere...

Also, as someone who passed on having kids because of books like “The Population Bomb” (if you haven’t read it, the title says it all) I’m OK with the population stabilizing or maybe shrinking a bit — but we’re about to see quite a few people starve — and I’m very not OK with that.