Regensburg 2025 – wissenschaftliches Programm

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SOE: Fachverband Physik sozio-ökonomischer Systeme

SOE 10: Focus Session: Large Language Models, Social Dynamics, and Assessment of Complex Systems

SOE 10.7: Vortrag

Donnerstag, 20. März 2025, 17:00–17:15, H45

Disentangling individual vs. collective contributions to polarization in political voting — Gavin Rees and •Edward Lee — Complexity Science Hub, Vienna, Austria

Politics around the world exhibit increasing polarization, most visibly demonstrated by rigid voting configurations in legislatures. This impacts their ability to seek effective compromise and pass impactful legislation. The crux of polarization is the emergence of a unidimensional ideological axis that primarily determines voting. Yet, legislative bills often negotiate multiple issues, whose effects may add up or compete for any individual vote. We develop a model inspired from statistical physics that accounts for voters with multi-dimensional preferences that can be linearly combined to generate coalitions. This allows us to capture higher-order correlations beyond those captured in direct spin-spin interaction models. As a result, the model is dramatically simpler, fits the data better, and is more interpretable than canonical maximum entropy or utility-based models from political science for large voting bodies. We study roll-call voting in US Congress, and we find coexistence of non-polarized with polarized modes. We show how increased partisan polarization is the contribution of two terms: increased party-line voting by the individual plus depletion of votes that would elicit complex, bipartisan response. Both decrease over time, but the latter falls much faster. Thus, we propose a more principled way of tracking the emergence of polarization at the level of the voter and the collective issues the many vote on.

Keywords: voting; polarization; congress; entropy