My daughter asked me the same question this morning!
I also would appreciate reading the replies.
My daughter asked me about it too. I told her about the lab rat experiments we did in college. When too many of them were confined in a too small of a space, they got crazy and exhibited anti-social behaviors. I am serious. I believe this explains some of the problems with large cities.
Occupations that promote liberal views, different lifestyles promote different values, higher education leads to more secular values and an elitist mentality...etc.
I could go on, but I don't want to write a big analysis...lol
Urban = black and/or union.
Suburban/rural = white non-union.
That's step 1.
The WHY may be more difficult.
Far be it from me to suggest IQ.