Ideal Point Estimation

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. The concept of ideal point estimation integrates theoretical ideas from spatial models in economics and political science with measurement theory from psychometrics. Theoretically, the core idea is that a low-dimensional latent preference structure explains behavioral choices and 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. The major focus of modern Ideal point estimation work has thus been on establishing empirical spatial models with a theoretical basis for the estimated locations of actors for use in empirical studies requiring continuous latent measures of 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 environments, 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. Meanwhile, 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 rapidly, producing an array of measurement techniques related to ideal point estimation applied to numerous topics in political science, especially political ideology.