Voting Behavior, Coalitions and Government Strength through a Complex Network Analysis

We analyze the network of relations between parliament members according to their voting behavior.<br>In particular, we examine the emergent community structure with respect to political coalitions<br>and government alliances. We rely on tools developed in the Complex Network literature to explore<br>the core of these communities and use their topological features to develop new metrics for party<br>polarization, internal coalition cohesiveness and government strength. As a case study, we focus<br>on the Chamber of Deputies of the Italian Parliament, for which we are able to characterize the<br>heterogeneity of the ruling coalition as well as parties specific contributions to the stability of the<br>government over time. We find sharp contrast in the political debate which surprisingly does not<br>imply a relevant structure based on establised parties. We take a closer look to changes in the<br>community structure after parties split up and their effect on the position of single deputies within<br>communities. Finally, we introduce a way to track the stability of the government coalition over<br>time that is able to discern the contribution of each member along with the impact of its possible<br>defection. While our case study relies on the Italian parliament, whose relevance has come into the<br>international spotlight in the present economic downturn, the methods developed here are entirely<br>general and can therefore be applied to a multitude of other scenarios.