Distributive consequences of plurality voting versus proportional representation

Employing a game-theoretic model of electoral competition, Myerson (1993, American Political Science Review 87 ( 4 ): 856–869) finds that both single-winner plurality voting (PV) and proportional representation (PR) lead to identical equilibrium campaigning strategies, with platform inequalities increasing as the number of political competitors rises. Using the same model, this paper derives and compares the resulting post-election income distributions and associated Gini coefficients. Key findings include: (1) The identical campaigning strategies under PV and PR lead to considerably different post-election income distributions. (2) For any given number of competing parties, PV exhibits comparatively higher inequality. (3) Inequality rises with the number of parties in both electoral systems but increases more rapidly under PV. Notably, when PV is fixed at two parties (Duverger’s law), once the simulated number of parties exceeds five, PR exhibits slightly higher inequality, challenging the belief that PR is inherently the more equal electoral system.