Ideal Point Estimation

Abstract

Political scientists have used ideal point estimation primarily to operationalize spatial models of politics, which requires measuring the preferences of actors within a conceptual latent space. Ideal point estimation integrates theoretical ideas from spatial models in economics and political science with measurement theory from psychometrics. Theoretically, the core concept is that a low-dimensional latent preference structure explains behavioral choices or judgments of stimuli. Empirically, the aim is to estimate models of the latent spatial properties of data that can predict an observed set of choice and response data. A central concern of ideal point estimation work in political science has been the generation of meaningful measures of the intervals between the coordinates of actors and the stimuli to which they respond. Accordingly, the primary focus of modern ideal point estimation work has thus been to create empirical spatial models with a theoretical foundation for the estimated locations of actors for use in studies requiring continuous measures of latent preferences. The early development of this work began as part of the study of legislative voting, chiefly among members of the US Congress. This work then extended to other legislative and judicial voting contexts, and eventually to a wide array of different political choice behavior that can be understood through the lens of the spatial models, from speech to social media activity. Related approaches have long been applied to survey data with sophisticated methods to generate measures of actors’ latent preferences, including from multiple data sources. Numerous applications have emerged in the last several decades and continue to grow in number, producing an array of measurement techniques related to ideal point estimation applied to numerous topics in political science, especially political ideology. This bibliography is limited mainly to work focused on or contributing to the literature on the measurement of ideal points, but several applications of ideal point estimation are included due to their influence on this methodological literature.