Well, I had heard of Ravenstein's laws either, but now I have. To save you some embarrassment at a cocktail party sometime, I am pasting them below: But remember, a little knowledge is sometimes more dangerous than none. Or something like that.
Ernest George Ravenstein: The Laws of Migration, 1885.
"1) Most migrants only proceed a short distance, and toward centers of absorption.
2) As migrants move toward absorption centers, they leave "gaps" that are filled up by migrants from more remote districts, creating migration flows that reach to "the most remote corner of the kingdom."
3) The process of dispersion is inverse to that of absorption.
4) Each main current of migration produces a compensating counter-current.
5) Migrants proceeding long distances generally go by preference to one of the great centers of commerce or industry.
6) The natives of towns are less migratory than those of the rural parts of the country.
7) Females are more migratory than males."