The Big Sort: why the clustering of like-minded Americans is tearing us apart by Bill Bishop (Houghton Mifflin, 2008).
The simple answer to the question posed by the title is that “clustering of like-minded Americans” in particular cities, states and towns exacerbates political polarization and thus tears us apart. The key insight offered by Bishop is that polarization is the effect, not the cause. While it is hard to remember those days, in 2008 the U.S. was still a prosperous society. Throughout the 1990s and early 2000s, the economy was so strong that many of us could afford to move to our ideal location where people like us resided. Without always being conscious of it, we moved to places where the dominant culture reflected our values. According to Bishop, most of us ended up in highly homogeneous neighborhoods, places of worship, and organizations (although I think he over-generalizes). Nevertheless, he does have a lot of data and stories that point to the overall truth of his argument. He sheds some light on the decline of non-Evangelical Protestant churches, and also places some blame on the advertising community for our political polarization. The Big Sort is an interesting read that makes you rethink your assumptions.