Party System Polarization Trends: Measuring Change and Identifying Its Causes

• In Event: Polarization and Dimensionality in Advanced Industrial Societies

Abstract

Polarization, the stretch of political parties across the left-right ideological continuum, is one of the most important properties of party systems. Polarization has been shown to shape, (as well as reflect,) citizen voting behavior, government formation and durability, and ideological congruence between voters and governments. It is often interpreted as channeling citizen discontent democratically, but disruptively, into the electoral and legislative processes. Thus, an analysis of measurement and explanation of polarization trends seems especially appropriate to the 2018 APSA Conference theme of “Democracy and Its Discontents.”

Analysis of the party manifesto data since the 1950s suggests substantial decreases in polarization in a majority of economically developed countries and increases only in a few. Is this a real decline or a failure of the usual manifesto measures (RILE scores) to capture new aspects of party dispute? Or both? How does the recent rise in the appearance and support for populist, anti-globalization parties shape polarization? The paper uses CSES perception data, manifesto RILE scores (in two different ways,) and an alternative method of treating the MRG manifesto codes, (proposed by Simon Franzmann and André Kaiser,) to explore the similarities and differences in estimating polarization trends.

The paper then estimates the relative roles of movement in positions of specific parties, entry and exit of parties, and changing voter support for centrist or more extreme parties in producing polarization changes within countries. The conditioning effects of different electoral systems are examined. Manifesto-based and perception-based measures are compared.

Authors

• G. Bingham Powell, University of Rochester

• Sergio Jesus Ascencio Bonfil, University of Rochester