Aggregate Data, Ecological Regression, and Voting Transitions

Abstract

Abstract Voting data typically comprise the marginal distributions of votes cast at two successive elections. The fact that these obtain separately for many voting precincts or areas enables one to estimate the actual transition probabilities for movements between the options available to the voter at each election. An aggregated compound multinomial model is proposed. This allows log-linear dependence on various covariates and specifies a simple and illuminating structure of random effects. The information in such aggregated data is compared with that which would obtain had all of the transitions been observed. The model is applicable to many other types of aggregated data and meets many of the difficulties inherent in “ecological regression.” It is illustrated with an analysis of the British European election of 1984.