Moving on Quicksand: The Effect of Social Structural Changes on Party Policy Positions

This paper studies the impact of social structural changes on party positions in a two-dimensional space, through a quantitative analysis of a data set of party policy shifts and socio-economic variables. While the literature on cleavage voting has found evidence that citizens respond to changes in the positions of political parties, and the spatial competition literature has focused on the electoral and institutional causes of party policy shifts, very little attention has been paid to the social structural causes of those shifts. Rather than changes in the public opinion mood or average preference (endogenous to party strategies), I argue that changes in the actual size and configuration of social groups (mostly exogenous to party strategies) influence party positions, by modifying the perceived electoral gains and the incentives for party actors in the choice between traditional constituency and new catch-all strategies. In particular, changes in the class structure influence the position of parties on an economic dimension, while changes in agricultural employment, urbanization and education affect positions on a socio-cultural dimension, while no effect is found for recent increases in immigration. This study provides a contribution to the literature offering a novel empirical assessment of the relationship between social structure and party policy shifts. Moreover, modelling changes in a multidimensionality space, it represents a significant advancement on the standard use of a single left-right dimension, improving our understanding of party strategies in a longitudinal dynamic setting.