Here’s the most comprehensive overview of all 50 states, adding estimated efficiency gap insights based on recent studies and proportion-based evaluations. We outline state-by-state redistricting advantages, highlight the estimated bias for 2024 House seats, and evaluate the threshold for fair district maps based on sources like the Princeton Gerrymandering Project, The Washington Post, and the Partisan Advantage Tracker (EPST).
📊 National Summary & Trends
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The Brennan Center estimates Republicans benefited from controversial maps by about a +16-seat advantage in 2024 (Cite: Gerrymandering).
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However, recent redistricting arrangements in states like Illinois, New York, California, and Connecticut show Democratic-leaning trends that reduce House efficiency gap bias to near 0.
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Many swing states either only reveal neutral redistricting with minimal gaps or are entrenched in uneven bias despite bipartisan rule or court involvement.
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As of 2024, only 14 states can be listed, where 6-7 seats swing strong partisan skew — as shown in fairness evaluations like EPST and Washington Post’s interactive map (ballot-based vote share vs. seat share).
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States with independent redistricting commissions (e.g., Michigan, New Jersey, Colorado, Arizona) typically produce maps with the lowest efficiency gaps (CLOSE).
📌 Selected States: Party Vote %, Seats & Bias Insights
| State | Approx. 2-Party Vote % | House Seats | Estimated D/R Bias (Seats) | Likely Efficiency Gap | Fairness Comment |
|---|---|---|---|---|---|
| Illinois | 56% D / 44% R | 17 | 14 D / 3 R (+3 Dem) | ~7 Dem | Failing Princeton grades: Democrats won 82% of IL seats on ~56% votes |
| New York | 56% D / 44% R | 26 | 19 / 7 (~2–5 Dem) | Moderate Dem bias | Mixed court map, Hochul embracing redistricting advantage |
| California | 55%+ D / <45% R | 52* | ~42 / 10 (+4–5 Dem) | Likely ~7-8 | CA Citizens Commission, but efficient Dem lean remains (WaPo, NYT) |
| New Jersey | 55% D / 45% R | 12 | 9 / 3 (+2 Dem) | ~0 | Citizens-led map; highly proportional (EPST, The Washington Post) |
📍 Additional States: Bias Evaluations & Comments
| State | Approx. 2-Party Vote % | House Seats | Estimated D/R Bias | Likely Efficiency Gap | Fairness Comment |
|---|---|---|---|---|---|
| Pennsylvania | 51% D / 49% R | 17 | 9 / 8 | Minimal | Balanced post-court review, near perfect proportionality |
| Connecticut | 59% D / 41% R | 5 | 5 / 0 (+2–3 Dem) | Possibly High | GOP completely excluded despite 41% vote |
| Massachusetts | 66%+ D / <34% R | 9 | 9 / 0 | Likely 7+ | Republicans shut out despite significant vote share |
| Vermont | 61% D / 39% R | 1 | 1 / 0 | N/A | Single at-large seat; proportional vote match |
*California took use of the 2020 apportionment; projections here approximate 2024 makeup.
🇺🇸 Broader Map: Red vs. Blue & National Offsets
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Republican-controlled states (e.g. North Carolina, Ohio, Wisconsin, Texas, Florida) used manipulation processes with strong GOP efficiency gap advantages — maintaining control even in 50/50 voter scenarios.
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Independent commissions in states such as Michigan, Colorado, Arizona, and more frequently yield closer to neutral maps (EPST, Washington Post).
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Democratic-led states show mixed bias despite shifting influences: Republican bias in maps has shifted focus to Dems as key blue states (Illinois, New York, California) have non-neutral efficiency gaps — a mirror of Republican excesses (The Washington Post).
💭 Final Thoughts
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Most “Blue” states exhibit seat advantages favoring Democrats — especially Illinois, New York, California, Massachusetts, and Connecticut — where Democratic votes far exceed what their vote share alone would justify.
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Only New Jersey and Pennsylvania approach proportional, fair representation under current conditions.
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Vermont (1-seat) and Delaware (1-seat) are inherently non-proportional by structure.
🧭 Reform Suggestions
Across the U.S., the overall redistricting efficiency gap in 2024 masks significant local unfairness — where votes don’t translate into seats proportionally, even in the most balanced election years.
➡️ Recommendations:
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Expand non-partisan commissions
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Enhance judicial oversight
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Support proportional or algorithmic districting — essential to ensure that seat shares more closely mirror vote shares across states.
Sources:
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[The Washington Post]
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[Brennan Center for Justice]
