Partisan Dislocation Reveals Where Gerrymanders Split Neighborhoods

🔍 What It Measures

Introduces a fine-grained, precinct-level indicator called Partisan Dislocation that quantifies the extent to which electoral districts combine or split local communities of co-partisans in unnatural ways. The measure captures how district lines alter local partisan geography at the level of individual voters and neighborhoods.

🧭 How the Measure Is Calculated

• Partisan Dislocation is defined as the difference between the partisan composition of a voter’s geographic nearest neighbors and the partisan composition of that voter’s assigned district.
• Large differences signal instances where district boundaries carve up clusters of co-partisans (cracking) or combine them in atypical ways (packing).

📌 Key Findings

• The indicator works as both a local and a global signal of district manipulation, able to identify specific neighborhoods affected by boundary drawing as well as broader patterns across maps.
• It reliably flags classic gerrymandering tactics (cracking and packing) while remaining distinct from existing measurement approaches.
• Advantages include:
• Acting as a complement to simulation-based gerrymandering assessments,
• Pinpointing the particular precincts and neighborhoods most impacted by district design,
• Providing a transparent, spatially precise lens on representation that augments aggregate summary measures.

⚖️ Why It Matters

The measure can be used prospectively by map-drawers who aim to create districts that reflect underlying voter geography. However, applying this geographic fidelity can sometimes conflict with the goal of partisan fairness, highlighting a practical tension between preserving local community partisan composition and achieving equitable partisan outcomes.