Beyond the Median: Voter Preferences, District Heterogeneity, and Representation

Empirical studies of the connection between citizen preferences and legislator actions have largely focused on the preferences of a district’s average or median voter. While many theories suggest that preference heterogeneity should also affect this connection, few empirical analyses have rigorously tested claims about the distribution of individual voter preferences. In this paper, we use a unique set of individual-level proposition voting data from Los Angeles County that allows us to estimate the distribution of voter preferences, including the mean, median, and variance (heterogeneity), for various subsets of voters in each of 55 State Senate, State Assembly, and U.S. House districts in the county. We then develop measures of legislator ideology for each district based on Poole and Rosenthal’s NOMINATE scores. We use these data to test hypotheses about the relationship between district preferences, district heterogeneity, and legislator behavior. Regression analyses reveal that legislators’ roll call votes are more closely related to district mean preferences in homogeneous districts than they are in heterogeneous districts. Roll call votes of legislators from heterogeneous districts are better predicted by the mean preference of members of the legislator’s own party. Thus, in the presence of significant preference heterogeneity, we find that the convergence predictions of the median voter result fail to hold.