District level competition in Mexico’s chamber of deputies: an embedded analysis

Why does Mexico’s mixed legislative system diverge from Duverger’s Law? Rather than rehash cultural and historical explanations, we suggest two institutional factors – a fused ballot and compulsory voting laws – may explain this divergence. Cross-national evidence controlling for these factors suggests Mexico is not an outlier and that the fused ballot encourages multiparty district competition. The results also suggest ways reforms could bring competition closer toward Duvergerian expectations.

为何墨西哥的混合立法体制与迪韦尔热定律（Duverger’s Law）相悖？本文摒弃重复阐释文化与历史层面的成因，提出两项制度性因素——混合选票（fused ballot）与强制投票立法——或可解释这一偏差。控制上述因素的跨国实证研究表明，墨西哥并非异常值，且混合选票机制会推动选区层面的多党竞争。研究结果同时指出，可通过改革举措使选举竞争更贴近迪韦尔热定律的预期效果。