Facebook ethnicity and geography data reveals one interesting picture. Take a look at the spread of black and asian facebook users:
The areas most densely populated by asian and black facebook users (and all asian and black people in general since this data is practically the same as one from the US census) are pretty similar to what it was before – fifty years ago, a century ago.
What does it mean? People in general don’t like to change their areas of habitat. Even in America where almost everyone have a car, where all the country is densely stitched with superhighways and there are no legal restrictions to move anywhere, even in America people tend to live where their parents an parents’ grandparents lived.