Speaker:     Michael Fowlie and Mark C. Wilson
Affiliation: The University of Auckland
Title:       Electoral engineering through simulation
Date:        Tuesday, 25 Sep 2012
Time:        4:00 pm
Location:    Room 5115, Owen Glenn Building

We report on recent and ongoing work to optimize electoral system parameters (e.g., party vote threshold for MMP) with respect to the competing criteria of decisiveness/governability and proportionality/fairness of parliament. This uses both real data (hard to obtain) and extensive simulation with artificially generated societies. Models for the latter are also hard to find, and we solicit audience help. Some interesting computational issues arise.

This forms the mandatory public talk for Michael’s CS380 project.

Everyone welcome!

Speaker:     Shaun White
Affiliation: The University of Auckland
Title:       Strategic voting: overshooting and undershooting, and safe and unsafe strategic votes
Date:        Tuesday, 11 Sep 2012
Time:        4:00 pm
Location:    Room 5115, Owen Glenn Building

There are many situations in which mis-coordinated strategic voting can leave strategic voters worse off than they would have been had they not tried to manipulate.  We develop a framework for analysing the simplest of such scenarios, in which a set of strategic voters all have the same sincere preferences and all cast the same strategic vote, while all other voters vote sincerely.  We say a voter has `an incentive to vote strategically’ when they can manipulate the choice mechanism by voting strategically in unison with certain other voters who share their sincere preferences.  We classify mis-coordinations as instances of strategic overshooting (when the choice mechanism is anonymous, overshooting occurs when too many vote strategically) or strategic undershooting (too few vote strategically). If casting a strategic vote cannot inadvertently lead to overshooting or undershooting, we call it safe. We extend the Gibbard-Satterthwaite Theorem by proving that every onto and non-dictatorial social choice rule can be individually manipulated by a voter casting a safe strategic vote. All this is joint work with Arkadii Slinko.

Speaker:     Simona Fabrizi
Affiliation: Massey University (Albany)
Title:       Learning and collusion in new markets with uncertain entry costs
Date:        Tuesday, 28 Aug 2012
Time:        4:00 pm
Location:    Room 5115, Owen Glenn Building

This paper analyzes an entry timing game with uncertain entry costs. Two firms receive costless signals about the cost of a new project and decide when to invest. We characterize the equilibrium of the investment timing game with private and public signals. We show that competition leads the two firms to invest too early and analyze collusion schemes whereby one firm prevents the other firm from entering the market. We show that, in the efficient collusion scheme, the active firm must transfer a large part of the surplus to the inactive firm in order to limit preemption.

Paper written in co-authorship with Francis Bloch (Ecole Polytechnique) and Steffen Lippert (University of Otago).

Speaker:     Jack Stecher
Affiliation: Carnegie Mellon University (USA)
Title:       Expected Utility and Equilibrium with Subjective Choice Sets and Strategic Reporting
Date:        Monday, 25 Jun 2012
Time:        4:30 pm
Location:    Room 6115, Owen Glenn Building

This paper studies an economy where agents trade using a shared language, so that
they do not need to meet in person with goods physically present. Agents provide
vague descriptions of proposed net trades, which we interpret as arising either from
inherent limitations in what the agents can describe or from strategic presentations of
information. We construct a family of orders over terms in the language, arising from
an individual’s preferences over consumption as subjectively perceived, illustrate the
induced order’s properties, and show the constructive existence of competitive equi-
librium. Finally, we illustrate the relationship between the existence of a competitive
equilibrium obtained in the language and the one that would result from an interaction
involving perceived consumption sets.

Speaker:     Arkadii Slinko
Affiliation: The University of Auckland
Title:       Geometric properties of voting rules
Date:        Monday, 18 Jun 2012
Time:        4:00 pm
Location:    Room 6115, Owen Glenn Building

Each axiom of voting rules considered in Economics and Political Science reflects some notion of fairness, e.g., unanimity requires that, if all voters vote for a certain candidate, this candidate should be elected; anonymity requires that it does not matter who submitted which ballot; monotonicity requires that, if support of the winner of the election grows, she should remain the winner of the election.

In a completely different vein we investigate the geometric properties of voting rules. We define a graph on the set of all elections as vertices and colour them  in a such a way that two vertices have the same colour if and only if the corresponding elections have the same winner. We determine for which classic social choice rules the monochromatic components are connected, convex, etc.

This is a work in progress in co-authorship with Edith Elkind, Svetlana Obraztsova, Piotr Faliszewski.

Speaker:     Patrick Girard
Affiliation: The University of Auckland
Title:       Logical dynamics of belief change in the community
Date:        Monday, 21 May 2012
Time:        4:00 pm
Location:    Room 6115, Owen Glenn Building

In this paper we explore the relationship between norms of belief revision that may be adopted by members of a community and the resulting dynamic properties of the distribution of beliefs across that community. We show that  at a qualitative level many aspects of social belief change  can be obtained from a very simplistic model, which we call `threshold influence’. In particular, we focus on the question of what makes the beliefs of a community stable under various dynamical situations. Besides, we  consider refinements and alternatives to the `threshold’ model. The most significant alternative is to move to consideration of plausibility judgements rather than mere beliefs. We show first that some such change is mandated by difficult problems with belief-based dynamics related to the need to decide on an order in which different beliefs are considered. Secondly, we show that the resulting plausibility-based account results in a dynamical system that is non-deterministic at the level of beliefs. Nonetheless, the plausibility-based account lacks certain intuitively desirable features, such as the preservation of the transitivity.

Speaker:     Patrick Girard
Affiliation: The University of Auckland
Title:       Ceteris paribus reasoning and preferences
Date:        Monday, 7 May 2012
Time:        4:00 pm
Location:    Room 6115, Owen Glenn Building

Ceteris Paribus clauses in reasoning are used to allow for defeaters of norms, rules or laws, such as in von Wright’s example “I prefer my raincoat over my umbrella, everything else being equal”. I offer an analysis in which sets of formulas S, embedded in modal operators, provide necessary and sufficient conditions for things to be equal in ceteris paribus clauses. I’ll talk about how ceteris paribus preferences can be formalised and discuss questions that arise with the formalisation, and propose some solutions.

Speaker:     Arkadii Slinko
Affiliation: The University of Auckland
Title:       MMP review: what are the issues and what are the options?
Date:        Monday, 26 Mar 2012
Time:        4:00 pm
Location:    Room 6115, Owen Glenn Building

In this talk I will outline the issues under consideration in the current review of the MMP voting system and outline the major options that can be chosen. I will try to explain the rational and major trade-offs made in the design of hybrid systems like MMP. From this point we will start a discussion on particular issues. This will hopefully start the process of preparation of a submission to the Electoral Commission on behalf of the Centre.