Migration flows follow predictable patterns based on opportunity and networks.
Ravenstein's 1885 laws from British census data: most migrants move short distances, migration proceeds in steps, and each current produces a counter-current. All three still hold.
In practice
- Most moves are short: a household leaves a village for the nearest town before anyone leaves for the capital.
- A migration corridor established by one cohort is used by the next, which is why flows follow networks rather than opportunity alone.