Given the preponderance of depression, anxiety, frustration, hopelessness, loneliness, suicide, poor self-care, etc that seems to take hold in "high standard of living" communities, you may be conflating measures of a strong economy with measures of a healthy and durable society.

The 20th century west made an all-in bet that those things might be correlated, and coaxed (and sometimes coerced) others into joining, but it's not clear that the bet is paying off or that it will.

Assume birthrates fall and remain below replacement globally. Is the percentage zero?

A below-replacement birth rate does not stabilize at zero percentage workforce participation unless the population actually drops to zero.

And worrying about 'what will happen if human population actually drops to zero' is like worrying about commuter traffic congestion on Mars.

> And worrying about 'what will happen if human population actually drops to zero' is like worrying about commuter traffic congestion on Mars.

Why not? I don't think it will happen, but at the same time, I don't want to say anything about human behaviour without stating assumptions. If you think (as do I) that there is always some point above zero population at which birth rates do stabilise, then it's valuable to examine what exactly that would entail.

It sounds like we agree the point exists somewhere - we could extend your example to the whole Earth's population becoming 2 and the population becoming (8 bn / 2)% more productive. Why can't we extend it to the population becoming 1?

Because fertility has feedback loops. When there are two people left on earth, their decision to have children or not will not be based on any of the economic or social concerns that we currently face.

It's a completely different situation, and none of the shit we are arguing about applies to it. There's a fundamental difference between running and meeting the long-term needs of a human society of 10 billion people and a human society of 10.

The mathematics you're using is the same reduction to absurdity that leads a manager to believe that nine women can deliver one baby in one month.

But under the current system, the wealth generated by those productivity gains is captured by a tiny fraction of the population. Elon Musk has many children, but most people are caught in the rat race.

I'll always argue that what we've been seeing for the last few centuries is a local-maxima, and we're in a rut. We've hyper-optimized food and other goods production at the expense of a bunch of things, that we're only now realizing.

The environment is the familiar one, but also at the expense of health safety (PFAS/lead/etc), and at the expense of our societal makeup. Perhaps the optimal distribution of labor for food production isn't 0.00001%, but would be good for growth and other intangibles if it were say 0.05%.