The research on the factors that incentivise participation appears to form a puzzle within Political Science. This article addresses a more specific issue, the relationship between the disproportionality of electoral systems and voter turnout. The most established hypothesis assumes a positive relationship between proportionality and electoral participation. This hypothesis seems to have been confirmed for industrialised countries with advanced democracies. We test this hypothesis using the case of the Spanish Congress of Deputies, one of such democracies. The Spanish case offers methodological advantages that make it ideal for isolating the impact of the examined variable. However, the hypothesis is not confirmed, adding another piece to a puzzle that apparently is not resolved in the literature.
