Word count: 8,915 Existing work on the effects of electoral reforms suggests that decreasing the costs of voting may exacerbate rather than reduce representational biases in turnout. We argue that some electoral institutions may have more uniform mobilization effects than previously thought and exploit the sequential introduction of postal voting in Switzerland to analyze how an exogenous decrease in voting costs affects the political and socio-demographic composition of turnout in direct

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... ation. In contrast to previous studies we find that postal voting mobilizes equally along many dimensions including individuals' political knowledge, employment status, and religious denomination. Although it does mostly activate supporters of leftist and centrist parties, less politically interested individuals, and high earners, these changes have only limited effects on the overall turnout composition and are unlikely to affect referendum outcomes. Our results alleviate some of the concerns about the negative side effects of electoral reforms on political choice in large electorates.