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Federal and Unitary Systems - AP Comparative Government and Politics Study Guide

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

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Getting Started

This chapter explores the vertical organization of state power through federal and unitary systems. A federal system is a constitutional arrangement that divides power between national and subnational levels of government, granting some local autonomy. A unitary system concentrates governing authority in a single, national government. We will compare the federal states of Mexico, Nigeria, and Russia with the unitary states of China, Iran, and the United Kingdom to understand why states choose these structures and how power distribution can change over time.

What You Should Be able to Do

  • Describe the key features of federal systems in Mexico, Nigeria, and Russia.

  • Describe the key features of unitary systems in China, Iran, and the United Kingdom.

  • Explain the purposes of adopting a federal system, such as managing ethnic cleavages and providing local services.

  • Explain the purposes of adopting a unitary system, such as promoting policy uniformity and efficiency.

  • Compare how power has become more centralized or decentralized over time in both federal and unitary states.

Key Developments & Analysis

The choice between a federal and unitary structure is a fundamental decision about how a state governs its territory and population. Federal systems are often adopted to manage large or diverse countries, while unitary systems are designed for efficiency and national cohesion. However, the formal structure does not tell the whole story, as the actual distribution of power is dynamic and subject to change.

Comparison of Federal Systems

DimensionMexicoNigeriaRussia
Primary RationaleTo manage a large territory and historically distinct regions.To accommodate and manage deep ethnic and religious cleavages among its many groups.To govern the world's largest landmass and incorporate numerous ethnic minority republics.
Degree of Local AutonomyState governments have constitutional authority over local matters, including some social and educational services.The 36 states possess significant powers, but their autonomy is often challenged by the national government's control over oil revenue.Regional autonomy has been significantly curtailed over time, with the national government centralizing power, especially under Vladimir Putin.
Reserved National PowersThe national government controls foreign policy, national security, and currency, among other exclusive powers.The national government controls the military, foreign policy, and the critically important oil and gas sector.The national government maintains authority over defense, foreign affairs, and the federal budget, with increasing influence over regional policy.

Comparison of Unitary Systems

DimensionChinaIranUnited Kingdom
Primary RationaleTo maintain strong, centralized control under the Chinese Communist Party (CCP) and ensure national unity.To concentrate power within a theocratic framework, ensuring that all policy aligns with the principles of the Islamic Republic.A long historical tradition of a single, sovereign parliament governing the entire state.
Policy UniformityPolicies are set by the national leadership in Beijing and implemented uniformly, though some economic decentralization exists.The Supreme Leader and other national institutions create uniform policies based on their interpretation of Islamic law.Historically, policies were highly uniform. Devolution has created significant policy variation in areas like education and health.
Mechanisms of ChangePower has been decentralized for economic purposes (e.g., Special Economic Zones) but remains highly centralized politically.Power remains highly concentrated at the national level with no significant decentralization movements.Devolution, the transfer of power to regional governments, has decentralized power in response to nationalist movements.

Drivers of Power Shifts

Driver of ChangeFederal Example: RussiaUnitary Example: United Kingdom
Internal Ethnic CleavagesRussia has used the presence of ethnic minorities as a reason to both grant and, more recently, curtail regional autonomy to prevent separatism.In response to strong nationalist identities in Scotland, Wales, and Northern Ireland, the UK devolved specific powers to regional legislatures.
External ActorsRussia's national government has centralized power partly as a response to perceived threats from other countries and international organizations.Membership in the European Union (a supranational organization) required the UK to accept shared authority on certain policies, a form of external influence.

Data & Organization Tools

Concept-to-Countries Matrix

System Type: Federal States

ConceptMexicoNigeriaRussia
System TypeFederalFederalFederal
Primary PurposeTerritorial ManagementEthnic Cleavage ManagementTerritorial & Ethnic Management

System Type: Unitary States

ConceptChinaIranUnited Kingdom
System TypeUnitaryUnitaryUnitary
Primary PurposeCentralized Party ControlTheocratic UnityHistorical Tradition

Power Dynamics

ConceptCountry ExampleDescription
Centralization in a Federal StateRussiaThe national government has systematically reduced the autonomy of subnational units.
Decentralization in a Unitary StateUnited KingdomThe central government has voluntarily transferred (devolved) powers to regional governments.

Institution–Actor–Function Map

Level of GovernmentKey Institution/ActorCore Function in Power Distribution
National (Federal States)National Legislature (e.g., Russia's Federal Assembly)Reserves powers for the national government (e.g., defense, foreign policy).
Subnational (Federal States)State/Regional Governments (e.g., Nigeria's 36 states)Exercise a degree of local autonomy in supplying social and educational services.
National (Unitary States)Central Government (e.g., China's State Council)Concentrates power to create uniform national policies and ensure efficient policymaking.
Subnational (Unitary States)Local/Regional Bodies (e.g., Scottish Parliament)Implement national policy; may exercise devolved powers granted by the central government.

Country Anchors Bank

  • Nigerian Federalism: The division of Nigeria into 36 states is a direct attempt to manage intense ethnic and religious competition by giving different groups control at the local level, though this is complicated by national control over oil wealth.

  • Russian Centralization: Under Vladimir Putin, Russia has recentralized power by changing the way regional governors are selected and creating federal districts to oversee the regions, reducing the autonomy inherent in its federal system.

  • Mexican States: Mexico's 31 states and federal district have constitutional authority over local services like education, demonstrating the division of power in a federal system, even if power has historically been dominated by the national level.

  • UK Devolution: The creation of the Scottish Parliament, Welsh Senedd, and Northern Ireland Assembly are prime examples of decentralization within a unitary state, where the central government transfers power to subnational bodies in response to internal pressures.

  • Chinese Unitary Control: The Chinese Communist Party (CCP) maintains ultimate authority over all levels of government, ensuring uniform political and social policy across the country, which is a hallmark of a centralized unitary system.

  • Iranian Theocracy: Iran's unitary system concentrates all sovereign power in the national theocratic institutions, particularly the Supreme Leader, leaving little to no autonomous power for subnational governments.

  • Supranational Influence on the UK: Prior to Brexit, the UK's membership in the European Union meant that some policy decisions were made by a supranational organization, illustrating how external actors can influence the distribution of power within a state.

Skill Snapshots

  • Comparison: Nigeria uses its federal structure to manage ethnic diversity, whereas China uses its unitary structure to enforce national unity under a single party. The UK has decentralized power through devolution, while Russia has centralized power within its federal system. Mexico's formal federalism contrasts sharply with Iran's highly centralized, theocratic unitary state.

  • Mechanism: Adopting a federal system → allows subnational governments to provide local social and educational services. The process of devolution in the UK → grants specific legislative powers to regional assemblies to address nationalist demands. Centralizing appointment power over regional governors in Russia → strengthens the national government's control over subnational units.

  • Change Over Time: In the United Kingdom (unitary), the baseline was a highly centralized state. Key changes include the devolution of significant powers to Scotland and Wales. A key continuity is that the Westminster Parliament remains legally sovereign and could, in theory, revoke these devolved powers.

Common Misconceptions & Clarifications

  • Federalism is not the same as democracy. Russia is a federal state with an authoritarian regime.

  • Unitary systems are not inherently authoritarian. The United Kingdom is a unitary state with a democratic regime.

  • Decentralization can occur in unitary states. The UK's devolution of power is a clear example of decentralizing power without adopting a federal constitution.

  • "Local autonomy" in federal states is not absolute. The national government always reserves significant powers, such as national defense and foreign policy.

  • All federal systems are not equally decentralized. The actual degree of subnational autonomy varies greatly, as seen in the comparison between Mexico and the more centralized Russia.

One-Paragraph Summary

States organize power vertically through either federal or unitary systems. Federal states like Mexico, Nigeria, and Russia constitutionally divide power between national and subnational governments, often to manage diversity and confer local autonomy over services. In contrast, unitary states like China, Iran, and the UK concentrate power at the national level to promote policy uniformity and efficiency. The choice of system reflects a state's approach to governing its territory and people. However, these structures are not static; the distribution of power can change over time. Both federal systems (like Russia) and unitary systems (like the UK) can centralize or decentralize authority in response to internal pressures, such as ethnic cleavages, or the influence of external actors like supranational organizations.