Robin Hanson:

World population is widely projected to peak around 2050-90 at roughly 9-11B, with ~40% living in Africa. World population would then decline. But how long, and how far? The median respondent in my Twitter polls expects a population revival ~2150, and only 15% see population falling below 2B. So most expect this to be a mild and temporary problem. But I’m not so sure. In this post, I’ll review some possible scenarios.

First, let’s set some context. Starting in France ~250 years ago, the number of children born to each woman in her lifetime, her “fertility”, consistently fell as incomes rose. Though some say this “demographic transition” is most closely connected to female education and access to contraception/abortion than to income. The most proximate causes I see are the high status of career success requiring high youthful efforts, a preference for fewer higher status kids, and an increasing taste for leisure.