A Coalitional Game-Theoretic Model of Stable Government Forms with Umpires

Abstract

In this paper a government form is modeled as an effectivity function scheme (EFS) i.e. a parameterized family of effectivity functions having admissible (strong) weight-profiles as the relevant parameters. Working in a 2-jurisdiction outcome space we show that the existence of umpires is consistent with strong core-stability of a neo-parliamentary or mixed semi-presidential government form provided that the majority formation rule is collegial.