The Ideological Congruence Controversy

TLDR

Research on ideological congruence has used diverse measurement approaches and data, and recent studies find no significant difference between single‑member district and proportional representation systems, with associations between electoral rules and congruence remaining robust across methods. The article investigates how alternative measurement approaches and data sets explain recent findings, concluding that time‑period differences—not measurement differences—drive the observed results. The study compares major alternative measurement approaches and data sets to assess their impact on ideological congruence findings. All three major approaches show that the association between election rules and ideological congruence has declined over the past decade, mainly because plurality parties in single‑member district elections have converged toward the median.

Abstract

Focusing on the left-right scale as a summary measure of citizens’ and representatives’ preferences, a growing body of literature has used a variety of approaches and data in measuring positions of citizens and representatives. The most recent studies, contrary to previous ones, show no significant difference between ideological congruence in single member district (SMD) and proportional representation (PR) electoral systems. This article examines the major alternative measurement approaches and data sets, finding that recent results are due to differences in time period, not differences in measurement approach. The associations between election rules and ideological congruence are relatively robust to various measurement approaches, as are estimations of the causal processes shaping ideological congruence. The association between election rules and congruence has declined in the past decade, as shown by all three major approaches, due primarily to convergence toward the median of plurality parties in the SMD elections.