The median voter model in public choice theory

The changing perception by public choice theorists about the relevance of the median voter model is a result of excessive extrapolation of the conclusions of theoretical models to the real world. Early in the 1970s the median voter model was often accepted as implying that the output produced in the public sector was what was most preferred by the median voter. This claim is excessive because the median voter model is only a model of demand aggregation under majority rule and has little to say about the supply side of the public sector. In the late 1970s many scholars identified several circumstances under which the model would not apply in theory, but these critiques of the model were often viewed as reasons to abandon the median voter model altogether. The model went from having excessive claims that made the model appear to be more powerful than it really is to excessive claims that made the model appear to be less powerful than it really is. These latter claims were often in response to the earlier claims rather than to the model, appropriately applied.Pointing out that the model might not be valid under some circumstances in no way implies that the model is never valid. In fact, this paper has reviewed strong arguments, both empirical and theoretical, suggesting that the median voter model is a good approximation of demand aggregation in the public sector for many issues. One paper will not change the opinions of public choice theorists on the median voter model. But the argument given here is that there is a large amount of theoretical and empirical evidence supporting the median voter model as a good foundation for the development of the theory of public sector demand. Once the overly ambitious claims that have been made for the model are set aside, the median voter model is in a good position to provide a base for the development of a theory of political structure that is analogous to the theory of market structure in economics.