Abstract
<title>Abstract</title> <p>Biproportional representation improves aggregate party proportionality by constraining district-level allocations through canton-wide party entitlements. This article examines how those constraints affect candidate outcomes in a personalized list system. It distinguishes classic seat reversals from the broader set of party--district entitlement changes generated by biproportional allocation. When a party's district entitlement changes while candidate rankings remain fixed, the electoral threshold moves within the local list. The article analyses the 2023 Zurich cantonal election through an exact mechanical counterfactual comparing the observed biproportional seat matrix with independent district-level Webster allocation. District magnitudes, party votes, the legal quorum, candidate votes, and candidate rankings are held constant. Fourteen of 188 party--district cells differ, representing seven seat transfers and fourteen candidate status changes. Seven of the 180 parliamentary seats, or 3.9 percent, would have had a different occupant. Two transfers produce discordant seat allocations in which a locally weaker party receives more seats than a stronger party. Biproportionality reduces the Gallagher index from 2.64 to 1.73 and the Loosemore--Hanby index from 4.81 to 2.55. Six transfers correct aggregate party-seat totals, while one reflects additional territorial redistribution. Vote gaps across the shifted candidate thresholds vary substantially, showing that mechanically equivalent status changes can cross either narrowly or clearly differentiated local rankings. The findings reveal a measurable trade-off between aggregate proportionality and local allocation continuity. JEL Classification: C63 , D71 , D72</p>