Small Aggregates, Big Manipulation: Vote Buying Enforcement and Collective Monitoring

Vote buying is widespread in developing democracies despite the secret ballot. What explains its resilience? I argue that brokers condition future payments on published electoral results to enforce these transactions and that this is effective at inducing voters' compliance only when the results of small voting groups are available. Using monitors' and citizens' reports of electoral manipulation and survey data from Colombia, I find a robust negative correlation between the average polling station size and various measures of vote buying. Evidence from a variety of identification strategies suggests that this relationship can be attributed to aggregate monitoring sustaining these transactions and not to the brokers' increased ability to identify compliers or other characteristics of places where polling stations are small.