议会投票网络中的联盟结构与极化：来自意大利议会的证据
Coalition Structure and Polarization in Parliamentary Voting Networks: Evidence from the Italian Parliament
AI总结：
本文提出基于网络的分析框架，用于研究议会投票网络中的联盟结构与极化现象，通过分析意大利议会的投票数据揭示了联盟结构对极化的影响及个体投票行为与系统结构的关系。
摘要：
在多党制系统中确保立法问责需要能够揭示实际投票行为的定量工具，而不仅仅是正式政党归属。我们提出了一种基于网络的框架，用于分析议会动态在多个尺度上，捕捉联盟结构、群体凝聚力和个体影响。该方法应用于意大利议会超过400万次投票表达，涵盖三个政府任期（2018-2021年）。该方法结合了网络模块度、投票距离度量和中介中心性，以映射集体决策的结构。利用该框架，我们表明系统层面的极化，通过网络模块度捕捉，系统性地取决于联盟结构而非联盟规模。技术政府表现出悖论性的全球极化程度较低，尽管有更广泛的正式支持，这反映了结构上混合的投票模式，而非统一的集团。在极化问题如移民上，网络极化强烈依赖于反对派的碎片化或凝聚力，即使执政联盟投票一致。中介性分析显示，中介角色高度集中，仅有约2%的议员在社区之间起结构桥梁作用。社区检测进一步揭示了未在声明联盟中显现的隐含联盟。该框架仅依赖于公开的投票记录数据，使分析可重复且直接适用于任何具有透明投票记录的议会。通过将个体投票行为与系统层面的结构联系起来，该方法为立法投票网络和联盟监测的比较分析提供了定量基础设施，能够系统评估立法行为。
英文摘要：
Ensuring legislative accountability in multi-party systems requires quantitative tools that reveal actual voting behavior beyond formal party affiliations. We present a network-based framework for analyzing parliamentary dynamics at multiple scales, capturing coalition structure, group coherence, and individual influence. Applied to over 4 million vote expressions from the Italian Parliament across three government formations (2018-2021), the methodology combines network modularity, voting distance metrics, and betweenness centrality to map the structure of collective decision-making. Using this framework, we show that system-level polarization, as captured by network modularity, varies systematically with coalition structure rather than coalition size. Technical governments display paradoxically lower global polarization despite broader formal support, reflecting structurally mixed voting patterns rather than unified blocs. On polarizing issues such as immigration, network polarization depends strongly on the fragmentation or cohesion of the opposition, even when the governing coalition votes cohesively. Betweenness analysis reveals that mediator roles are highly concentrated, with only about 2% of parliamentarians acting as structural bridges between communities. Community detection further uncovers implicit coalitions that are not apparent from declared alliances. The framework relies exclusively on public roll-call data, enabling reproducible analysis and direct applicability to any legislature with transparent voting records. By linking individual voting behavior to emergent system-level structure, the methodology provides quantitative infrastructure for comparative analysis of legislative voting networks and coalition monitoring, enabling systematic assessment of legislative behaviour.
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