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Lattice Algorithms Reveal Dangers of Ignoring Spatial Data in Gerrymanders
Insights from the Field
gerrymandering
lattice
Monte Carlo
redistricting
isoperimetry
Voting and Elections
Pol. An.
1 archives
1 text files
Dataverse
Lattice Studies of Gerrymandering Strategies was authored by Kyle Gatesman and James Unwin. It was published by Cambridge in Pol. An. in 2021.

🔎 How Voters Are Placed on a Grid

A new theoretical approach models voters on a lattice where districts are formed by partitioning that lattice. This framework makes the spatial distribution of voters explicit and supports construction of districts subject to population and connectivity constraints.

🛠️ Three New Algorithms That Build Pro-Gerrymander Districts

  • Introduces three novel algorithms designed to produce equal-population, connected districts that advantage the gerrymanderer.
  • Each algorithm explicitly incorporates spatial voter distributions when drawing district boundaries.
  • Algorithms are evaluated against the practical requirement that districts remain contiguous and population-balanced.

🎲 Why Monte Carlo Simulations Are Applied

  • Voter models on the lattice include probabilistic population fluctuations at the local scale.
  • Those stochastic fluctuations enable the use of Monte Carlo techniques to study variability and the likely impact of different gerrymandering strategies across many simulated realizations.

📊 What the Comparisons Reveal

  • Direct comparisons across the three algorithms show distinct performance profiles in how effectively they secure partisan advantage.
  • Methods that ignore spatial data can produce disconnected districts—configurations that are typically legally prohibited.
  • The study assesses the performance of geometric detectability tests, focusing on isoperimetric quotient measures, and evaluates how well these tests detect the constructed gerrymanders.

âť—Why It Matters

This lattice-based framework makes spatial structure central to the design and evaluation of redistricting strategies. The combination of spatially-aware algorithms and Monte Carlo sampling offers a systematic way to compare gerrymandering tactics and to test the strengths and limits of geometric metrics (like isoperimetric quotients) used to flag illicit district shapes.

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