In countries that hold equality is important, clustering occurs between groups because of polarizing factors such as religion, wealth or ethnocentrism. Clustering is often considered an enriching part of free cultures in which one can visit a Chinatown or a French quarter for restaurant choices. Other sociologists assert that clustering of like minded individuals leads to political polarity and intolerance of contrary opinions, as the United States has allegedly been trending since the 1950s.
- Bill Bishop, Robert G. Cushing, The Big Sort: Why the Clustering of Like-Minded America Is Tearing Us Apart (Houghton Mifflin Harcourt, 2009) http://books.google.com/books?id=nLNVd8ZkW0UC&source=gbs_navlinks_s ISBN 0-547-23772-3, ISBN 978-0-547-23772-5
See also 
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