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Boundary Changes and Competitive Seat Exclusion in Singapore’s 2025 Redistricting: An Ensemble-Based Test

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  • Goh, David

    (University of Toronto)

Abstract

We test whether Singapore's 2025 electoral redistricting produced a statistically anomalous allocation of competitively contested territory. Using a hypergeometric permutation test, we examine the 114 subzones that changed constituency between the 2020 and 2025 general elections. Among the 52 subzones originating from competitive 2020 constituencies (PAP vote share < 55%), zero ended up in competitive 2025 constituencies—against an expected value of 3.2 under random redistribution (Fisher’s exact p = 0.012). The anomaly follows a specific pattern: the new competitive seat (Jalan Kayu SMC) was seeded from stronghold populations, while dissolved competitive constituencies were absorbed into safe districts. A complementary MCMC ensemble analysis using GerryChain finds that while Singapore’s boundaries are extreme outliers in geometric compactness, this is consistent with administrative logic rather than partisan gerrymandering. We conclude that while the GRC block-vote remains the primary seat-to-vote bonus mechanism, redistricting serves as a secondary mechanism for managing competitive communities.

Suggested Citation

  • Goh, David, 2026. "Boundary Changes and Competitive Seat Exclusion in Singapore’s 2025 Redistricting: An Ensemble-Based Test," SocArXiv p7q2m_v1, Center for Open Science.
    • Handle: RePEc:osf:socarx:p7q2m_v1
    DOI: 10.31219/osf.io/p7q2m_v1
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