Mining and Analyzing the Italian Parliament: Party Structure and Evolution

TL;DR

This study analyzes Italian Parliament roll calls over time using clustering and network analysis to reveal increasing fragmentation and evolving community structures among Parliamentarians without prior knowledge of party membership.

Contribution

It introduces a multi-method approach combining multidimensional scaling, clustering, and network analysis to detect political fragmentation and community evolution in Parliament data.

Findings

Increasing fragmentation of political parties over time

Effective detection of community structures without prior party knowledge

Insights into the temporal evolution and cohesiveness of Parliament groups

Abstract

The roll calls of the Italian Parliament in the XVI legislature are studied by employing multidimensional scaling, hierarchical clustering, and network analysis. In order to detect changes in voting behavior, the roll calls have been divided in seven periods of six months each. All the methods employed pointed out an increasing fragmentation of the political parties endorsing the previous government that culminated in its downfall. By using the concept of modularity at different resolution levels, we identify the community structure of Parliament and its evolution in each of the considered time periods. The analysis performed revealed as a valuable tool in detecting trends and drifts of Parliamentarians. It showed its effectiveness at identifying political parties and at providing insights on the temporal evolution of groups and their cohesiveness, without having at disposal any knowledge about political membership of Representatives.