2022-2024 Editions
2022-2024 Editions
Time and place: Thursday, 25 August 2022, 11am-noon, room 260-319 [level 3 of Sir OGGB]
Speaker: Matthew Ryan [AUT]
Title: Stochastic Choice [Lecture 1 of n]
Abstract: This talk will introduce stochastic theories of choice. Such theories are ubiquitous in mathematical psychology and were also intensively studied by economists in the 1950s-1970s. Since then, they have persisted within economics mainly in the guise of discrete choice models in econometrics (such as logit and probit). However, in recent years there has been a resurgence in interest in stochastic choice models amongst economic theorists. This talk is intended as a simple introduction to the field and, if there is interest, a starting point for a mini-series of talks on classical models and recent developments. The talk(s) will also present a few open questions and hopefully stimulate some research ideas. The field embraces a lot of empirical work on the econometrics of choice. While I’m not an econometrician, I will try to point to developments in that area, and certainly to interesting empirical questions, so hopefully the topic may also be of interest to the econometrically inclined. There are now quite a few publicly available datasets with which to explore various empirical questions. And of course…there will be donuts.
Time and place: Wednesday, 31 August 2022, 3pm-4pm, room 260-325 [level 3 of Sir OGGB]
Speaker: Matthew Ryan [AUT]
Title: Unanimity under Ambiguity (joint work with Simona Fabrizi, Steffen Lippert [UoA] and Addison Pan [XJTLU])
Abstract: This paper considers a binary decision to be made by a committee — canonically, a jury — through a voting procedure. Each juror must vote on whether a defendant is guilty or not guilty. The voting rule aggregates the votes to determine whether the defendant is convicted or acquitted. We focus on the unanimity rule (convict if, and only if, all vote guilty), and we consider jurors who share ambiguous prior beliefs as in Ellis (2016). Our contribution is twofold. First, we identify all symmetric equilibria of these voting games. Second, we show that ambiguity may drastically undermine McLennan’s (1998) results on decision quality: unlike in the absence of ambiguity, the ex-ante optimal symmetric strategy profile need not be an equilibrium; indeed, there are games for which it is possible to reduce both Type I and Type II error starting from any (non-trivial) equilibrium. Finally, we explain the significance of these results for our on-going experimental work on voting behaviour.
Time and place: Wednesday, 14 September 2022, 3pm-4pm, room 260-317 [level 3 of Sir OGGB]
Speaker: Matthew Ryan [AUT]
Title: The Venerable Logit Model: Origins and Recent Developments [Lecture 2 of n=3]
Abstract: This is “Lecture 2 of n” in the mini-series on stochastic choice. The logit model is perhaps the most familiar model of stochastic choice to economists. Last time I introduced the Luce model – which is essentially equivalent to logit – and showed that it is characterised by the Choice Axiom. This talk will describe some other classical theoretical results on the logit model, including their proofs (which are elementary): two alternative characterisations, and the result that every logit model is also an independent random utility model. The latter theorem is important for econometric applications. Then I’ll describe some striking new theoretical results on (generalisations of) the logit that have appeared in the last couple of years. I’m still getting to grips with these so there should be plenty of scope for discussion and debate (and correction of the speaker’s errors!), and hopefully even some avenues for further research.
Time and place: Wednesday, 21 September 2022, 3pm-4pm, room 260-317 [level 3 of Sir OGGB]
Speaker: Matthew Ryan [AUT]
Title: n=3! [as of Lecture 3 of n=3]
Abstract: This will be the last in the mini-series of talks on stochastic choice. For the finale, I’ll discuss classical characterisations of the random utility (RU) model: one for random choice functions defined on an arbitrary domain of menus and one for functions defined on the universal domain (i.e., all non-empty subsets of X). These characterisations have been the focus of recent empirical work that seeks to test the RU hypothesis on laboratory or field data. I’ll briefly touch on this empirical work, but I’m not an econometrician so happy to listen to subsequent talks by anyone who can provide deeper insight into this work.
Time and place: Wednesday, 26 October 2022, 3pm-4pm, room 260-317 [level 3 of Sir OGGB]
Speaker: Yunjie Shi [PhD Candidate in Economics, UoA]
Title: On Sequential and Simultaneous Contributions under Incomplete Information [based on Bag and Roy (2011)]
Abstract: Under incomplete information, voluntary contributors to a public good hold independent private valuations for the public goods and are uncertain about each other’s valuations. When released to the sequential move game, early contributors are likely to be cautious in free-riding on future contributors. This presentation will focus on the sufficient condition under which the sequential game generates strictly higher expected contribution than simultaneous move games. A Bayesian setting model is adopted where there is an arbitrary number of agents and a fairly general distribution of types. I will go over some details about this conventional model as well as other striking new theoretical results on the sequential move public goods provision problem. Hopefully, some detailed extensions of my future research will also be presented. Happy to hear your comments and suggestions.
Time and place: Wednesday, 2 November 2022, 3pm-4pm, room 260-317 [level 3 of Sir OGGB]
Speaker: Debasis Bandyopadhyay [UoA]
Title: Crime Against Women in the Unified Growth Theory
Abstract: The UN data reveal that the crime against women (CAW) relative to total homicide display an inverted-U-shaped pattern against GDP per capita. We argue that the interaction of technological advancement and the politics of women's rights contributes to the evolution of gender inequality and that systematic gender imbalance in power provides a clue to understanding that observation. Our argument involves answering two questions. First, how does technological progress affect women's welfare in the macroeconomy? Second, what are the marginal impacts of the liberal political groups favoring women's rights? We answer them in a model where political conflicts about women's rights increase CAW. The model integrates conflict theories, developed by Esteban and Ray (2008, 2011), and the Unified Growth Theory of Galor and Weil (2000) and adds a gender lens to discern nontrivial implications for CAW. In the model, as technology advances, the value of women relative to men increases. If politics resist women's rights to education, gender inequality and CAW may increase at the initial stages of technology development. However, as technology advances sufficiently, gender inequality may decrease to strengthen the political group favoring women's rights, eventually lowering CAW. Numerical simulations reveal new insights for understanding cross-country differences in economic development and identifying new development traps arising from the political contest for choosing institutions for women's rights.
Time and place: Wednesday, 9 November 2022, 3pm-4pm, room 260-317 [level 3 of Sir OGGB]
Speaker: Stan Wang [PhD Candidate in Computer Science, Massey U]
Title: Multi-agent Learning with Decision Markets
Abstract: Decision markets are mechanisms to elicit and aggregate information to optimise decision-making. In the presentation, we will introduce a multi-agent system where a principal needs to decide between multiple alternative actions. Contextual information about the outcomes of the actions is distributed over multiple self-interested agents. The principal uses a decision market to reward these agents to reveal their information. We present simulations that demonstrate that with a proper reward, agents can learn to use their information to make accurate reports about the outcomes, and thereby learn to help the principal to make good decisions. To provide a proper reward, the principal needs to use a stochastic decision rule to select the action. However, this is not necessarily in the interest of the principal. We therefore also analyse strategies that are learned when the decision rule is deterministic and therefore the rewards are not proper. Finally, we discuss a mechanism that allows the principal to keep the decision-making process efficient and deterministic. Our simulations show that in this mechanism, the principal can provide proper incentives to elicit and aggregate all relevant information without using the realised outcome to determine the reward.
Time and place: Wednesday, 23 November 2022, 3pm-4pm, room 260-317 [level 3 of Sir OGGB]
Speaker: Danny Kwon [PhD Candidate in Economics, UoA]
Title: On the Salience of Privacy on Digital Platforms
Abstract: Users of digital platforms do not concern themselves with privacy issues until those are brought to their attention. Digital platforms have control over how visible privacy protection is to the users, by adjusting the transparency settings of data-collecting applications. In this presentation, I discuss the work I have done so far with respect to modelling the interactions between users, developers, and platforms given platforms' ability to control their privacy transparency setting in a duopoly market. I highlight some findings with respect to developer participation, and what this implies for user outcomes. This work is still ongoing, with the identification of each platform's user mass being the critical roadblock.
Time and place: Wednesday, 30 November 2022, 3pm-4pm, room 260-317 [level 3 of Sir OGGB]
Speaker: Matthew Ryan [AUT]
Title: Voting Behaviour with an Asymmetric Loss Function: Understanding the Experimental Evidence (joint work with Simona Fabrizi, Steffen Lippert [UoA] and Addison Pan [XJTLU])
Abstract: This talk discusses joint work with Simona Fabrizi, Steffen Lippert and Addison Pan. There is a small literature that tests binary voting behaviour in the laboratory – think of voting in a jury trial (but without discussion between jurors). Most of these experiments use symmetric loss functions – both types of error (convicting the innocent and acquitting the guilty) receive the same penalty – even when the unanimity rule is used to determine the outcome (i.e., the defendant is acquitted unless all jurors vote guilty). There is one extant study (Anderson et al., 2015) that employs a loss function with a higher penalty for convicting the innocent, and its results show by far the largest difference between the data and the theoretical prediction. We have conducted two more voting experiments involving an asymmetric loss function. This talk discusses our results, as well as those of Anderson et al. (2015), and assesses the prospects of reconciling the data with theory.
Time and place: Tuesday, 7 March 2023, 11am-12pm, room 260-6115 [level 6 of Sir OGGB]
Guest Speaker: Moon Duchin [Tufts University]
Title: Metrics of Electoral Fairness
Abstract: Social choice theory, as it crystallized in the 1950s, is centered on axiomatics: principles of the fair and reasonable functioning of democratic systems, which in turn sets up theorems about what combinations of properties are possible or not possible. (For instance, monotonicity properties generally hold that a hypothetical change in preferences that is favorable to some candidate should not hurt their electoral prospects.) Though these are often called fairness criteria, they can seem somewhat detached from the elements of elections that lead to public sentiment of fair and unfair systems. Similarly, the computer science community that works in algorithmic fairness has developed a suite of fairness axioms for algorithms that has been criticized as not capturing what really matters. In this talk I will discuss notions of fairness in elections, particularly the kinds intended for practical use---and I'll talk about my experiences with implementation, in policy and legal settings.
Time and place: Tuesday, 14 March 2023, 11am-12pm, room 260-6115 [level 6 of Sir OGGB]
Speaker: Arkadii Slinko [UoA]
Title: Gazing at the Universe of Parliament Choosing Rules
Abstract: The first-past-the-post (FPP) divides the country into districts. On the other hand, proportional representation (PR) rules treat the country as the only district. These are the two extremes in the world of parliament choosing rules. Each of them has its own logic based on the concept of representation with both having positive and negative features. We investigate this logic and describe several ways in which we may try to alleviate the negative features of FPP and PR without sacrificing the positive ones. This idea leads us to creating the hybrid voting systems, one of which is the mixed-member-proportional system (MMP) that New Zealand is using today. We look at the ways it can be further improved. We also look at the voting systems that can emerge in the future with the advances of computer technology, in particular, those based on the idea of creation not geographic but virtual districts - an old idea of Charles Dodgson that will soon become feasible within the limits of our computational capabilities.
Time and place: Wednesday, 19 April 2023, 11am-12pm, room 260-6115 [level 6 of Sir OGGB]
Guest Speaker: Ashutosh Dinesh Thakur [NUS]
Title: Endogenous Institutional Stability
Abstract: In many organizations, members need to be assigned to certain positions, whether these are legislators to committees, executives to roles, or workers to teams. In such settings, the design of the assignment procedure becomes an institutional choice that is influenced and agreed upon by the very members being assigned. Will these agents seek to reform the assignment procedures by voting in favor of some alternative allocation over their current allocation? I explore this question of institutional stability by bringing together matching theory and social choice. I introduce majority stability - i.e., institutional stability under majority rule - and juxtapose it with other voting rules an organization might use to resolve internal conflict. Institutional stability is undermined by correlation across agents' preferences over positions, as the resulting envy enables a decisive coalition to arise endogenously to change the institution. For extremely correlated preferences, I establish a Chaos Theorem wherein there exists a majority-approved agenda from any matching allocation to any other allocation. Nevertheless, I show that institutions are robust to intermediate correlation across preferences under majority rule, in sharp contrast to plurality rule (i.e., popular matching, studied in computer science). Given the prevalence of (super-)majority rules in practice, this suggests why we observe institutional stability.
Time and place: Tuesday, 2 May 2023, 11am-12pm, room 260-6115 [level 6 of Sir OGGB]
Speaker: Matthew Ryan [AUT]
Title: Revealed 'Luce rationality' (joint work with José Rodrigues-Neto and James Taylor [both ANU])
Abstract: The Luce (a.k.a. Logit) model is a standard formalism for describing stochastic choice behaviour. This paper explores its empirical signature: the properties of choice behaviour which are necessary and sufficient for representation by a Luce model. This signature is well known in two special cases. If choice is observed from all choice sets that can be constructed from a given (finite) universe of alternatives, then Luce’s (1959) IIA Axiom provides the required signature. If choice is only observed from the binary menus then the Product Rule condition is necessary and sufficient. Both of these results are classical. More recently, Echenique and Saito (2019) and, independently, Ahumada and Ülkü (2018) showed that a condition known as Cyclical Independence provides the required empirical signature when choice is observed from an arbitrary collection of choice sets. We adapt results from the (closely related) literature on Harsanyi’s “common prior” problem to refine this characterisation of the Luce model. Our results are useful for (i) designing efficient tests for Luce rationality; and (ii) constructing optimally informative choice sets for experiments, where it is usually only feasible to observe behaviour for a restricted number of choice situations.
Time and place: Tuesday, 9 May 2023, 11am-12pm, room 260-6115 [level 6 of Sir OGGB]
Speaker: James Brown [Honours Student in Economics, UoA]
Title: A Market for a Signal of Authenticity on a Social Media Platform
Abstract: In recent times, social media platforms Twitter, Instagram, and Facebook have introduced paid-subscription products that grant users access to certain features (Beykpour & Gupta, 2021; Reuters, 2023). This includes the famous blue checkmark appearing adjacent to the username of paying subscribers after they have undergone a process to verify authenticity. Prior to this, the blue checkmark was only granted to users of public interest to mitigate impersonation (Twitter, n.d.). Instead of acting as a symbol of high public interest, the blue checkmark now functions as a signal that a user has been verified as human. It is interesting to examine the effect of such signals in the context of social media with influencers who promote products on behalf of marketers.
Time and place: Tuesday, 1 August 2023, 10am-11am, room 260-6115 [level 6 of Sir OGGB]
Speaker: Addison Pan [UoA]
Title: An Overview of Funding Opportunities Available to Research Centres Based at the UoA
Abstract: Dr Addison Pan, in her new role as the International Networks Manager in the International Office at UoA, will give an overview of funding opportunities available to support research activities within research centres, such as the CMSS, in the context of various initiatives the UoA is adhering to, partnering with other institutions overseas and diverse networks.
Time and place: Tuesday, 29 August 2023, 10am-11am, room 260-6115 [level 6 of Sir OGGB]
Speaker: Matthew Ryan [AUT]
Title: Mathematical Social Science in Data Analytics
Abstract: The purpose of this talk is to introduce social scientists to selected ideas from data analytics, and to sketch a possible research agenda. I’ll not be presenting any new results; nor will there be any data! The discussion will focus on the binary classification problem (including predictive risk modelling [PRM]): basic concepts and some standard theory. Such problems use data and statistical models to “classify” people/objects according to whether or not they fall into a specified category. I will then describe three theoretical issues in binary classification to which social scientists are well-equipped to contribute: (i) fairness and bias in classification; (ii) measuring accuracy in PRM; and (iii) explainability of such models. Hopefully the presentation will provoke some cross-disciplinary conversation, and even some actual research.
Time and place: Tuesday, 24 October 2023, 10am-11am, room 260-6115 [level 6 of Sir OGGB]
Guest Speaker: Matthias Blonski [Goethe-Universität Frankfurt]
Title: Cooperation of Asymmetric Players in the Repeated Prisoner's Dilemma
Abstract: We investigate the question under which conditions asymmetric players with differing payoff parameters cooperate in an infinitely repeated discounted Prisoner’s Dilemma. Starting from established theory for the symmetric case we generalize to two distinct criteria which differ in their prediction about whether the willingness or ability of the two different players to cooperate are substitutes or complements. Finally, we run experiments designed to disentangle which of these two criteria predicts better.
Time and place: Thursday, 9 November 2023, 2-3pm, room 260-325 [level 3 of Sir OGGB]
Guest Speaker: Vladimir Smirnov [U Sydney]
Title: Elimination Tournaments with Resource Constraints
Abstract: We consider T-round elimination tournaments where players have fixed and equal endowments. We provide conditions for the existence and uniqueness of a symmetric equilibrium for a general class of elimination tournaments. We show that the winner-take-all prize scheme and the same number of competitors in each group in each round ensure equal resource allocation across all rounds.
Time and place: Tuesday, 14 November 2023, 10am-11am, room 260-5115 [level 5 of Sir OGGB]
Speaker: Herbert Wu [Master Student in Economics, UoA]
Title: Pricing Under Fairness Concerns
Abstract: Eyster et al. (2021) proposed a monopoly pricing theory with consumer fairness. In their paper, they assumed that consumers have fairness concerns and dislike unfair prices. Then, when a price rises due to a cost increase, consumers partially misattribute the higher price to higher markup—which they find unfair. A monopolist anticipates this response and adjusts their pricing strategies accordingly. I want to extend this work, by considering the duopoly (competitive) case, to understand how these effects might affect duopoly pricing under fairness concerns in an inflationary scenario, i.e., when consumers might find it increasingly more difficult to attribute price hikes to true underlying increasing costs, or to higher markups.
Time and place: Thursday, 16 November 2023, noon-1pm, room 260-317 [level 3 of Sir OGGB]
Guest Speaker: Frank Stähler [University of Tübingen]
Title: Disentangling Frictions Across the World: Markups versus Trade Costs (joint work with Benedikt Heid, Universitat Jaume I)
Abstract: Standard methods to quantify how trade cost changes affect international trade abstract from market power. We develop a structural framework that allows us to quantify the evolution of aggregate bilateral trade costs and markups over time. With minimal assumptions, we can disentangle aggregate markup and trade cost changes from observed changes in trade flows. We apply our method to trade data between 1990 and 2015 for the world’s 100 largest economies. We find that across all country pairs, on average, bilateral aggregate markups have increased by 6.8% per year. Since bilateral aggregate trade costs have fallen, we find a strong negative correlation between observed trade cost and markup changes. Finally, our framework allows us to quantify how markups affect the welfare gains from trade liberalization. We find that, on average, welfare gains would be about a third larger if markups were constant.
Time and place: Tuesday, 20 February 2024, 10am-11am, room 260-315 [level 3 of Sir OGGB]
Speaker: Arkadii Slinko [UoA]
Title: Necklaces, Convexity and Condorcet Domains
Abstract: Fishburn's alternating scheme domains occupy a special place in the theory of Condorcet domains. Karpov (2023) generalised these domains and made an interesting observation proving that all of them are single-picked on a circle. However, an important point that all generalised Fishburn domains are maximal Condorcet domains remained unproved. We fill this gap and suggest a new combinatorial interpretation of generalised Fishburn's domains using black and white necklaces and white-convexity which provides a constructive proof of single-peakedness of these domains on a circle. We show that classical single-peaked domains, single-dipped domains and Fishburn domains belong to the same family of domains while single-crossing domains do not as they are not even single-peaked on a circle.
Time and place: Tuesday, 5 March 2024, 10am-11am, room 260-6115 [level 6, Sir OGGB]
Speaker: Yibin Li [PhD Candidate in Economics, UoA]
Title: Multi-issue Strategic Information Transmission with Partial Attention
Abstract: This paper studies a cheap talk model where senders having idiosyncratic private information about distinct issues can transmit information to receivers in either public or private communication modes. The informativeness of effective communications in equilibrium is positively affected by receivers' partial attention to those issues and negatively affected by senders' biases. We further provide insights for the welfare properties of those equilibria.
Time and place: Tuesday, 21 May 2024, 10am-11am, room 260-6115 [level 6, Sir OGGB]
Speaker: Michael Demetrius [Master Student in Economics, UoA]
Title: Task Allocation Without Authority
Abstract: I present a static model of what I call the Task Choice Game, for the 2-agent, 2-task case. In the Task Choice Game, individual agents decide how to allocate their (equal) working day over different tasks that must be collectively completed. Agents care about consumption, which is shared, and about their personal disutility of labour. I characterise envy-free equilibria for two types of preferences over tasks: specialisation (tasks as perfect substitutes) and variety (tasks as complements). I sketch a price mechanism which could deliver envy-free equilibrium allocations for large numbers of agents and tasks.