What are the most common redistricting methods used by countries besides the US?

1. How the World Actually Draws the Lines — Independent Commissions Lead the Pack

Many countries use independent or non‑partisan commissions to delimit electoral districts, placing technical and political responsibility outside single-party legislatures to limit manipulation. Comparative sources highlight that independent commissions are common in OECD countries and are promoted by organizations such as International IDEA, the Carter Center, and IFES; these commissions typically have statutory mandates, criteria like one‑person/one‑vote, contiguity, and compactness, and transparent procedures including public hearings and published maps ^{[2] [1]}. The shift toward commissions responds to critiques of partisan cartography and aims to introduce predictable, rule‑based delimitation. However, commission design varies: some are composed of career civil servants or electoral officials, others include judicial appointees or mixed political appointees; the composition and appointment rules materially affect neutrality. International guidance emphasizes both institutional insulation and clear, public criteria to make commissions operationally effective.

2. When Politicians Draw the Lines — Legislature Control Persists in Practice

Legislature‑driven redistricting remains a common model worldwide where elected bodies retain primary authority to define constituencies, often through ordinary law or special parliamentary committees. This model persists because it aligns with democratic accountability and legislative sovereignty, and in many countries the electoral map is a central political tool controlled by parties that win majorities. Sources note that advisory or backup mechanisms sometimes limit outright abuse — for example, legislatures may be required to follow statutory criteria or face judicial review — but the core risk of partisan bias remains higher than under independent commissions ^{[3] [1]}. The rule of law and active judicial oversight can mitigate excesses, yet outcomes depend on domestic courts’ willingness to apply substantive standards like equal population and non‑discrimination. Where courts are weak or politicized, legislature control often yields maps that entrench incumbency or majoritarian interests.

3. The Middle Path — Advisory and Backup Commissions as Safety Valves

A number of systems use advisory commissions that propose plans which legislatures can accept or modify, or backup commissions that step in if the primary political actors fail to agree. Countries such as those cited in comparative material use advisory bodies to produce neutral proposals grounded in technical criteria, while leaving final legal authority to elected institutions; backup commissions operate as a legislative fail‑safe to avoid deadlock ^[3]. These hybrid arrangements attempt to balance impartial technical expertise with democratic legitimacy, but they introduce potential tension: legislatures can ignore advice, and the legitimacy of backup interventions depends on clear triggers and transparent procedures. International commentators and manuals emphasize that hybrids work best when the advisory body’s output is publicly justified and when legal thresholds for legislative override are high, thereby preserving the advisory body’s influence without fully removing democratic control ^{[2] [1]}.

4. International Rules and Technical Principles — What Every Mapmaker Quotes

Across jurisdictions, redistricting is guided by a set of recurring technical principles—equal population (one person, one vote), contiguity, respect for administrative boundaries and communities of interest, compactness, and transparency. These norms appear consistently in comparative toolkits and software such as the Electoral Redistricting App promoted by International IDEA, and are echoed by multilateral actors seeking to standardize good practice ^{[2] [1]}. While these criteria are conceptually straightforward, they conflict in practice: maximizing population equality can fragment communities, strict compactness can ignore cultural ties, and respect for administrative lines may skew partisan balances. The trade‑offs require political judgment, which is why many systems embed criteria hierarchies and dispute resolution mechanisms; these design choices determine whether technical principles reduce or merely repackage political contestation.

5. What the Evidence Shows — Trends, Limitations, and Political Stakes

Comparative evidence indicates a global trend toward institutional safeguards—particularly independent commissions and clearer criteria—but outcomes remain contingent on design details and enforcement. Sources emphasize that independent bodies reduce opportunities for blatant gerrymandering but are not a panacea: appointments, mandate clarity, and legal remedies matter as much as formal independence ^{[4] [1]}. International NGOs and electoral assistance groups therefore prioritize capacity building, transparency, and civil society participation alongside legal reforms ^[2]. At the same time, domestic political actors sometimes resist reforms that would limit leverage over maps, framing independence as a loss of democratic control; such pushback underscores that redistricting is as much a political settlement as a legal engineering problem, and any reform must grapple with entrenched incentives and institutional complementarities ^{[3] [4]}.