Ideology and existence of 50% : Majority equilibria in multidimensional spatial voting models

Hervé Crès (1) , Utku Unver (2)

1 ECON - Département d'économie (Sciences Po)
2 Department of Economics

When aggregating individual preferences through the majority rule in an n-dimensional spatial voting model, the ‘worst-case’ scenario is a social choice conÞguration where no political equilibrium exists unless a super majority rate as high as 1−1/n is adopted. In this paper we assume that a lower d-dimensional (d < n) linear map spans the possible candidates’ platforms. These d ‘ideological’ dimensions imply some linkages between the n political issues. We randomize over these linkages and show that there almost surely exists a 50%-majority equilibria in the above worst-case scenario, when n grows to inÞnity. Moreover the equilibrium is the mean voter. The speed of convergence (toward 50%) of the super majority rate guaranteeing existence of equilibrium is computed for d = 1 and 2.

Domaines: Economies et finances

Hervé Crès, Utku Unver. Ideology and existence of 50% : Majority equilibria in multidimensional spatial voting models. 2005. ⟨hal-01065582⟩