Do legislative voting rules affect the diversity of policies observed across structurally similar political economies, and if so, to what extent? To what degree do these rules affect legislative compromise and the stability of the social optimum? Using a spatial model of political competition with single-peaked preferences, we examine these questions in static and dynamic political economies where changing proposed policies requires supermajority consensus. We develop three findings pertaining to equilibrium policies that are immune to change by any supermajority coalition. First, we find the number of equilibrium policies that exist as a function of the supermajority's size. This result implies that under supermajority rules, structurally identical political economies may implement very different policies. Second, we find the optimal level of compromise needed by a leader to ensure that her proposed policy is not defeated and establish that compromise decreases in the supermajority's size. Third, we identify the minimal supermajority rule that ensures the stability of the social optimum. We derive implications for political design, policy diversity, and political inclusiveness.
Mahajan, Aseem and Pongou, Roland and Tondji, Jean-Baptiste, Supermajority Politics: Equilibrium Range, Diversity, and Compromise (June 17, 2020). Available at SSRN: https://ssrn.com/abstract=3463765 or http://dx.doi.org/10.2139/ssrn.3463765