People Migrate To Similar Sized Cities

A new study of migration within the U.S. in PLOS One (funded by Mexico, Italy and the EU and conducted in London) makes the following main findings:

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. 

People already living in larger cities are less likely to migrate, but when they do, they are more likely to move to similarly sized large cities. . . .

[I]nternational migration follows a different pattern, with individuals more likely to head to a large city where they are perhaps more likely to find jobs, housing and other people of a similar culture.

From here. The threshold for city status in the study was 50,000 inhabitants.