Fair Maps
What would Missouri look like with "fairly" drawn districts? Browse community plans, compare metrics, and see how the current map stacks up against alternatives.
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How We Measure Fairness
No single metric captures "fairness" perfectly. Redistricting scholars recommend evaluating plans across multiple dimensions. Here are the metrics we use, each measuring a different aspect of what makes a district map fair.
Polsby-Popper Compactness
Measures how close a district's shape is to a circle using the formula 4π × Area / Perimeter². Scores range from 0 (highly irregular) to 1 (perfect circle). Higher scores indicate more compact, less gerrymandered shapes. Most real districts score between 0.15 and 0.45.
Reock Compactness
Compares a district's area to the area of its minimum bounding circle. A district that fills most of its bounding circle scores higher. This metric penalizes elongated or tentacle-shaped districts more than Polsby-Popper does.
Population Deviation
Measures how far each district's population strays from the ideal (total population / number of districts). The U.S. Supreme Court requires congressional districts to be as equal in population as practicable. Deviations under 1% are generally considered acceptable.
Efficiency Gap
Compares "wasted votes" between parties — votes cast for losing candidates and votes for winners beyond the 50%+1 needed to win. A large gap suggests one party's votes are systematically diluted. Proposed by legal scholars as a judicially manageable standard. Values over 8% are often flagged.
Mean-Median Difference
Compares the mean and median party vote share across all districts. In a symmetric distribution, these should be roughly equal. A positive mean-median gap for one party suggests their voters are "packed" into fewer districts, while the opposing party's voters are spread more efficiently. Values over 2-5% warrant closer scrutiny.
About These Comparisons
The baseline map is Missouri's current enacted congressional district plan, drawn by the Missouri General Assembly following the 2020 Census. Community plans are sourced from public redistricting tools like Dave's Redistricting App and are scored using the same metrics for apples-to-apples comparison.
Important: No metric is definitive proof of gerrymandering. Geographic constraints, the Voting Rights Act, and communities of interest all legitimately affect district shapes. These metrics are tools for informed discussion, not verdicts.