This Bill Bishop keynote speech discusses the way that American society has become self-selectively segregated based on similar backgrounds and lifestyles.
The author describes how, over time, the population of the United States has been consistently affiliating themselves with other individuals who have similar political and societal views. Using the geographical demographics regarding which regions of the country voted for which party in recent electoral campaigns, the speaker shows that like-minded people tend to reside in similar neighborhoods. He explains that, even unintentionally, individuals are more likely to reside in an area where all of the surrounding residents share similar political or moral beliefs.
This type of polarization has a negative impact on the societal, political and economical makeup of the country as there is less mingling of cultures and ideologies, which leads to the dissolution of a nation-wide sense of community.