https://www.sciencedaily.com/releases/2018/07/180706160629.htm

The study, published today in the open access journal PLOS ONE, looked at internal migration patterns across the USA, finding that the size of origin and destination cities play a crucial role in the behaviour of people who move from one place to another.

Inhabitants of smaller cities -- of fewer than 100,000 inhabitants -- are twice as likely to migrate than those of cities with a population greater than ten million. Those who do migrate are more likely to move to a city of a similar size.