IQ and living in New England: According to the General Social Survey, New England has the highest average IQ. Now, is this due to the intelligence of those born there, or those who have moved in? Let's call those who were born in New England and have stayed there "stayers"; those who were born there and left after age 16 for another region "leavers"; and those who lived in another region at age 16 and later moved to New England "comers." Here are the means of the three groups:
Stayers and comers, 104.3
Stayers and leavers, 104.0
So, both comers and and leavers are smarter than stayers, but they essentially cancel each other out. New England is more intelligent than other regions because their stayers are smarter than the stayers in other regions, plus the smart people they lose are replaced with smart peoplle who move in.