Does Unequal Representation Bias Policymaking? Quasi‐Experimental Evidence From the Italian Senate
2026-07-16
How does unequal representation affect policymaking? Existing research shows that overrepresented districts exert disproportionate influence over public policy, yet our understanding of the underlying sources of this advantage remains limited. I argue that increased representation can independently bias policymaking via two channels: a mechanical effect, whereby additional representatives increase a district's likelihood of shaping the legislative agenda, and a behavioral effect, whereby legislators intensify constituency‐oriented effort due to intra‐district competition. To test this, I leverage the quasi‐experimental setting created by the electoral rule of the Italian Senate (1994–2006), which allowed districts with similar population sizes to elect either one or two senators. Using a regression discontinuity design and comprehensive data on bill (co‐)sponsorship, I find evidence consistent with both channels. Examining policy outcomes, I do not find that unequal representation yields distributive benefits, but I do find suggestive evidence of a broader legislative advantage.