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EC228: Collective Decisions

  • Kirill Pogorelskiy

    Module Lecturer
15 CATS - Department of Economics

Principal Aims

In many economic and political environments, a group of individuals must make a decision that will affect all of its members. Examples abound, including voting in elections, juries, and corporate boards. How to aggregate individual preferences in an optimal way? How different decision-making procedures affect the collective outcomes? This module develops mathematical models to formulate and answer these questions in a precise way. It will provide students with an introduction to the theory of social choice, conventionally defined as the study of the decision-making behaviour of voters, politicians, and government officials from the perspective of economic theory. It can be considered as a bridge between economics and political science, an introduction into more advanced topics in political economy. As such the module has an important role in contributing to the achievement of the aims of the joint degrees in Philosophy, Politics and Economics (PPE) and Economics, Politics and International Studies (EPAIS). However, the module will also appeal to students taking degrees taught entirely within the Economics department, and others.

Principal Learning Outcomes

By the end of the module, students should be able to demonstrate a knowledge and understanding of public choice and the decision-making behaviour of voters, politicians and government officials from the perspective of economic theory.


The module will typically cover some of the following topics:

Voting as preference aggregation; the social choice approach. Voting rules: unanimity, simple majority. Problems of majority voting: cycling, Arrow’s impossibility theorem. Restrictions on preference profiles. The single crossing property. Gibbard-Satterthwaite Theorem, strategy-proofness. Voting with more than two alternatives: majoritarian methods, Condorcet extensions, and positional methods. The spatial model of elections. Majority rule core, global cycling, McKelvey’s chaos theorem. Game theoretic approaches; two party competition, median voter theorem. Agenda manipulation. Public choice in a representative democracy; voting over redistribution. Bargaining in legislatures. Public goods and collective action; paradox of voting. Voting with incomplete information; Condorcet Jury theorem.


Pre or Co-requisites
EC106 or EC107 or EC108+EC109 or EC131
Part-year Availability for Visiting Students
Available in the Autumn term (1 x test – 12 CATS)


Assessment Method
Coursework (20%) + 2 hour exam (80%)
Coursework Details
One 50 minute test (20%)
Exam Timing

Exam Rubric

Time Allowed: 2 Hours

Answer ONE question from Section A (40 marks) and ONE question from Section B (60 marks). Answer Section A questions in one booklet and Section B questions in a separate booklet.

Approved pocket calculators are allowed.

Read carefully the instructions on the answer book provided and make sure that the particulars required are entered on each answer book. If you answer more questions than are required and do not indicate which answers should be ignored, we will mark the requisite number of answers in the order in which they appear in the answer book(s): answers beyond that number will not be considered.

Previous exam papers can be found in the University’s past papers archive. Please note that previous exam papers may not have operated under the same exam rubric or assessment weightings as those for the current academic year. The content of past papers may also be different.

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