Today a twenty-something told me that she doesn't plan to have children because of climate change.

[Warpy]

92. Real estate and farm prices crashed in the 1920s

The birth rate cratered in the late 1920s and stayed very low until after WWII.

With the New Deal and the consumer society and decent pay for a day's work, things looked rosy enough that people in their late teens through their early 40s felt safe enough to have kids. This is the baby boom, not so much that women were having huge families, but that a large age range of women were finally having them after 20 years of not being able to afford to.

That's part of what's happening now. Wages have been depressed since the late 70s and kid in their prime child bearing years are often crushed by student debt. Few can afford children and the political situation is just one other disincentive.

It's not just in the US, ether. Pessimism about the future is holding down population growth in most developed countries.