Sociological studies have found this to happen pretty often. A (very readable) study of tipping points can be found in There Goes the Neighborhood (http://www.

Sociological studies have found this to happen pretty often. A (very readable) study of tipping points can be found in There Goes the Neighborhood (http://www.amazon.com/There-Goes-Neighborhood-Tensions-Neighborhoods/dp/0679724184 http://www.amazon.com/There-Goes-Neighborhood-Tensions-Neigh...).