The relationship between electoral systems and corruption in a large sample of contemporary democratic nations is analysed in this article. Whereas previous studies have shown that closed-list proportional representation is associated with greater (perceived) corruption than open-list PR, it is demonstrated here that this relationship fails to hold once district magnitude is considered. The theory underlying this study draws on work on ‘the personal vote’ that suggests that the incentives to amass resources – and perhaps even to do so illegally – increase with district magnitude in open-list settings but decrease in closed-list contexts. Extending this insight, it is shown that political corruption gets more (less) severe as district magnitude increases under open-list PR (closed-list PR) systems. In addition, once district magnitude exceeds a certain threshold – the estimates here are that this is as low as fifteen – corruption is greater under open lists than closed lists. Only at small district magnitudes (below fifteen) is closed-list PR associated with more corruption, as conventionally held. These results hold for alternative measures of corruption, for different sets of countries analysed, for different measures of district magnitude and regardless of whether the political system is presidential or parliamentary, and of the number of parties.

Using an objective measure of corruption in public works contracting, corroborating evidence is also presented from Italian electoral districts. In Italy's open-list environment in the period prior to 1994, larger districts were more susceptible to corruption than smaller ones.