150 years ago, 90% of Americans worked in agriculture. Today 2% do and we are better fed. Population growth or shrinkage cannot match productivity technology as the key factor in material quality of life.

Countries with falling populations will just need more robots. Mass immigration isn't going to help, but this is one of those problems easily solved with tech.

What you're talking about is the economic concept of "labor productivity". If we can use factories and automation to create the same amount of stuff with fewer people, then our productivity will rise. If it rises fast enough, then we could have more stuff per person even with fewer people working. Problem solved!

Except: Productivity growth has historically never been high enough to bail us out of the hole we're in, and it has been trending down in recent years for reasons we don't fully understand.

> our material abundance isn't particularly under threat from contraction of the work force.

I wish!