Comment by cyberax

In 2003 the average fertility rate was around 2.03

It started falling to 1.6 around 2008 ( https://www.macrotrends.net/global-metrics/countries/usa/uni... ) which coincided with the millennials getting into the child-bearing age. And the millennials are much more likely to live in cities, even though they don't want that: https://news.gallup.com/poll/245249/americans-big-idea-livin...