A spatial analysis of the XIII Italian Legislature

We present a spatial map of the Italian House during the XIII Leg-islature obtained by applying the Poole and Rosenthal methodology to roll call data. We obtain coordinates for almost all the 650 MPs that were on the House's °oor at the time, and we aggregate them according to parties. We ¯nd that voting patters generate basically a two dimensional political space. The ¯rst dimension represents loyalty to either the ruling coalition or the opposing one. The second dimension may describe differences at the constitutional level. This finding is consistent with the exceptional case of the party Northern League, which at the time did not belong to either coalition, and presented itself as a northern and anti-system party. Last, we compute the average dispersion of party coordinates along each dimension and compare them with the Rice index of cohesion, the agreement index (which takes into account abstention), and one other index we construct to account for absence from voting. We ¯nd that absence is significantly correlated with the dispersion of parties along the second dimension. We use this to motivate the importance of further analysis on the massive absence in Italian Parliament from voting sessions.