Structural Balance and Political Polarization
Over the past few decades, political polarization in American politics seems to be picking up momentum, with Republicans and Democrats separating ideologically. Jonathan Haidt and Marc J. Hetherington of the New York Times attribute this trend to the Republicans allying with the Religious Right and the Democrats allying with the Civil Rights Movement and the implications of these alliances, reasons which are completely valid, however this trend can also simply be explained by the balancing of the network over time. If you look at this graph, courtesy of the New York Times, one can clearly see that Republicans and Democrats have increasingly disliked each other, and that the trend has also increased in speed over the past decade and a half.
What does network structural balance have to do with the increase in partisanship? Well, according to Easley and Kleinberg, the authors of our textbook, a network progresses towards structural balance over time, ending when group X and group Y fully separate, with only positive connections within the groups and negative connections between the groups. Now obviously this cannot be 100% the case on such a large scale network, but it does seem as though Democrats and Republicans want less and less to do with each other over time.
During the presidencies of Carter, Reagan and Bush, this trend existed but did not pick up speed until the end of Clinton’s term into W.’s term. Structural balancing relies on changes over time, but these changes are ultimately driven by interactions between nodes on the graph. In the late 90s and early 2000s, use of the internet in the US grew tremendously, giving rise to easier interactions between the two groups, hence an increase in speed of the polarization trend.
Sources:
http://campaignstops.blogs.nytimes.com/2012/09/17/look-how-far-weve-come-apart/?_r=0
D. Easley and J. Kleinberg. Networks, Crowds, and Markets: Reasoning about a Highly Connected World.