The School of Economics invites you to a School Theory seminar by Juan Carlos Carbajal (University of New South Wales).

Cause and Effect in Political Polarization: A Dynamic Analysis

Co-authors: 

Steven Callander (Stanford University)

Abstract

Despite widespread public opinion that political polarization is driven by the electorate at large, the data shows that, at least in the case of the US, polarization of the ‘elite’ precedes polarization of the ‘masses’ by at least a decade. The evidence also indicates that both political actors and voters are more polarized today than in any previous period after the Civil War, and that the dynamic process is incremental over time. These three facts combined motivate several critical questions: What is causing elite and masses to polarize, and which way does the causality run between groups? What caused the staggered timing of political polarization? Finally, how does a dynamic process of polarization affect voting issues within each electoral cycle? To address these questions, we propose a simple mechanism to explain the progressive polarization of preferences in a spacial voting model and the co-movement and timing of elite and mass polarization. We consider a canonical model of electoral competition in a two-party system with preferences distributed across a one-dimensional policy space. We embed this framework into a model of repeated elections and make but one change to the canonical model: namely, we assume that voters update their ideal points from election to election by moving closer to the candidate they voted for in the previous election. Our new assumption on its own does not imply polarization. This, instead, is driven by interaction of the voters’ updating rule and the way strategic parties respond to voters. Parties first converge, and then progressively polarize. Voters polarize only after parties do, although they eventually catch up. Our implications can at least in part explain the dynamics of polarization exhibited in the US. Perhaps more relevant for our purposes, we uncover a clear mechanism for how polarization occurs. Parties start close to the middle of the policy spectrum and progressively diverge. Extreme citizens initially converge and then diverge in their policy preferences.