Existence of a ‘structurally stable’ equilibrium for a non-collegial voting rule

This essay shows that, for any non-collegial voting rule, σ, there exists an integer, s(σ), with this property: if the policy space, W, has dimension no greater than s(σ), then there exists a profile of smooth utilities on W, such that the core for σ at this profile is non-empty and ‘structurally stable’ under sufficiently small perturbation. We also show how we may compute s(σ) for an arbitrary rule. This material is based upon work supported by NSF grant SES-84-18296, to the School of Social Sciences, University of California at Irvine. An early draft was written while the author was Sherman Fairchild Distinguished Scholar at the California Institute of Technology. Thanks are due to Kenneth Shepsle, Dick McKelvey and Gary Cox for helpful comments, to Michael Chwe and Shaun Bowler for research assistance, and to Derek Hearl and Ian Budge for permission to make use of unpublished data.