by sfab358 | May 21, 2018
Speaker: Addison Pan (University of Auckland)
Title: “A Note on The Pivotality Condition”
Date, Time and Venue: Wednesday, 23 May 2018, 14:00-15:00, 260-319 [Business School Building, Level 3]
Abstract: This note provides simple derivations of the equilibrium conditions for different voting games with incomplete information. In the standard voting game à la Austen-Smith and Banks (1996), voters update their beliefs only based on the probability that they are pivotal. However, in voting games such as those in Ellis (2016) and Fabrizi and Pan (2017), given a closed and convex set of priors, the ambiguous averse voters select the prior from this set in a strategy-contingent manner. Therefore, it is shown in this paper that in ambiguous voting games the conditional probability of being pivotal alone is not sufficient to determine each voter’s best response.
Everyone welcome!
by sfab358 | May 6, 2018
Speaker: Arkadii Slinko (University of Auckland)
Title: “What Do Multiwinner Voting Rules Do? Some Simulations Over the Two-Dimensional Euclidean Domain”, joint work with Edith Elkind, Piotr Faliszewski, Jean-Francois Laslier, Piotr Skowron and Nimrod Talmon
Date, Time and Venue: Wednesday, 9 May 2018, 14:00-15:00, 260-319 [Business School Building, Level 3]
Abstract: We visualize aggregate outputs of several multiwinner voting rules—SNTV, STV, Bloc, k-Borda, Monroe, Chamberlin–Courant, and PAV—for elections generated according to the two-dimensional Euclidean model. We consider three applications of multiwinner voting, namely, parliamentary elections, portfolio/movie selection, and shortlisting, and we use our results to understand which of these rules seem to be best suited for each application. In particular, we show that STV (one of the few nontrivial rules used in real high-stake elections) exhibits excellent performance, whereas the Bloc rule (also often used in practice) performs poorly. We also visualise three approximation algorithms for the computationally hard Chamberlin–Courant and Monroe rules. Our results show that the best approximation algorithms on offer (one of which is introduced in this paper) can be safely used instead of the original rules themselves.
Everyone welcome!
by sfab358 | Feb 18, 2018
Speaker: Piotr Faliszewski (Krakow)
Date, Time and Venue: Monday, 26 February 2018, 15:00-16:00, CaseRoom4/260-009 [Business School Building, Level 0]
Abstract: We start from examples of multiwinner voting rules, then dwell on a particular class of those rules, called committee scoring rules, which we consider in detail from axiomatic, algorithmic and experimental perspective. We promise beautiful pictures!
Everyone welcome!
by sfab358 | Feb 12, 2018
Speaker: Han Bleichrodt (Erasmus University Rotterdam and ANU)
Date, Time and Venue: Friday, 23 February 2018, 12:00-13:00, room 260-6115 [Business School Building, Level 6]
Title: Testing Hurwicz Expected Utility
Abstract: Gul and Pesendorfer (2015) propose a new theory of ambiguity, they dub Hurwicz expected utility (HEU). HEU is the first axiomatic theory that is consistent with most of the available empirical evidence on decision under uncertainty. We show that HEU is also tractable and a particular subclass can readily be estimated and tested. We do this by requiring the probability weighting functions in the HEU representation to come from a two-parameter family. We investigate two predictions of HEU. The first prediction is that ambiguity aversion is constant across different sources of ambiguity. We investigate this utilizing the data of Abdellaoui et al. (2011). We observe support for it in their most extensive data set, but not in the other data set. The second prediction is that ambiguity aversion and first-order risk aversion (Segal and Spivak, 1990) are positively correlated. We perform an experiment to test this prediction. As the positive correlation revealed in the data is only slight to fair we conclude the evidence of a positive relation between ambiguity aversion and first order risk aversion is not conclusive.
Everyone welcome!
by sfab358 | Oct 23, 2017
Speaker: Matthew Ryan (AUT)
Date, Time and Venue: Thursday, 26 October 2017, 2:00-3:00 pm, room 260-323 [Business School Building, Level 3]
Title: The Condorcet Jury Theorem: An Introduction
Abstract: Back in August, Simona Fabrizi presented her work with Addison Pan on the so-called “Jury Paradox”. The present talk provides an introduction to some of the background literature on group decision-making. The “Condorcet Jury Theorem” is an 18th century result due to the Marquis de Condorcet, which anticipates modern notions of the wisdom of crowds. It is also important in political theory as a rationale for democratic decision-making. The theorem asserts that (under suitable conditions) a group of relatively uninformed voters will make better decisions by majority rule than a single expert deciding unilaterally, provided the group is large enough. We introduce Condorcet’s result and its limitations, as well as a few extensions. Condorcet assumed “sincere” voting, while the modern research on group choice requires that votes be cast “rationally” – that is, the profile of votes should be an equilibrium (in the sense of Harsanyi) of the voting game. It is well-known that sincere voting need not be rational in this sense. Does the essence of the Jury Theorem survive strategic voting? Come along and find out!
Everyone welcome!
by sfab358 | Aug 2, 2017
Speaker: Rajiv Sarin (University of Exeter)
Title of the talk: “A Model of Satisficing”
Date, Time and Venue: Thursday, 17 August 2017, 2:00-3:00 pm, room 260-323 [Business School Building, Level 3]
Abstract: “We build a model of satisficing behaviour. We explicitly introduce the payoff the decision maker expects from a strategy, where this expectation is adaptively formed. This valuation of a strategy is differentiated from her satisficing level which is taken to be the payoff the agent expects from her best outside option. If the agent receives a payoff above her satisficing level she continues with the current action, updating her valuation of the action. If she receives a payoff below her satisficing level and her valuation of the action falls below her satisficing level she updates both her satisficing level and what she expects from the strategy. We show that in the long run, all players satisfice. In individual decision problems, satisficing behaviour results in cautious, maximin choice. In games like the Prisoner’s Dilemma and Stag Hunt, they converge to cooperative outcomes. In other games, such as canonical public good games, they converge to (selfish) Nash equilibria.”
Bio: Rajiv Sarin is Professor of Economics at the University of Exeter. He is a theorist whose research has appeared in such leading journals as American Economic Review, International Economic Review, Games and Economic Behavior and Journal of Economic Theory.
Everyone welcome!
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