Urban populations increase with industrial and economic development.
Urbanisation and economic development are strongly associated historically, though the relationship is not universal in timing or direction, and substantial urbanisation without contemporaneous growth has occurred. The causal direction is disputed: cities may drive development as much as follow it.
In practice
- A country's cities absorb its productivity growth and its housing crisis in the same decades.
- A region that industrialises finds its rural population halves within two generations without anyone having planned a migration.