We host market design seminars for researchers.
*All times are Japan Standard Time (JST).
*Unless otherwise mentioned, the seminars will be held online using Zoom (pre-registration system).
*Presentations are in ENGLISH.
*Please refrain from taking pictures, recording audio and video.
*Please do not reproduce the contents or share the Zoom joining URL with a third party.
Please use the following link for registration.
*Registration is required only for the first time. The same meeting URL can be used for this UTMD seminar series.
[May 20, 2022] Di Feng (University of Lausanne (HEC))
Date & Time: 2022/5/20 (Fri) 15:30-17:00
Title: A Characterization of the Coordinate-Wise Top-Trading-Cycles Mechanism for Multiple-Type Housing Markets
Abstract: We consider the generalization of the classical Shapley and Scarf housing market model of trading indivisible objects (houses) (Shapley and Scarf, 1974) to so-called multiple-type housing markets (Moulin, 1995). When preferences are separable, the prominent solution for these markets is the coordinate-wise top-trading-cycles (cTTC) mechanism. We first show that on the subdomain of lexicographic preferences, a mechanism is unanimous (or onto), individually rational, strategy-proof, and non-bossy if and only if it is the cTTC mechanism (Theorem 1). Second, using Theorem 1, we obtain a corresponding characterization on the domain of separable preferences (Theorem 2). Finally, we show that on the domain of strict preferences, there is no mechanism satisfying unanimity (or ontoness), individual rationality, strategy-proofness, and non-bossiness (Theorem 3).Our characterization of the cTTC mechanism constitutes the first characterization of an extension of the prominent top-trading-cycles (TTC) mechanism to multiple-type housing markets.
[Mar. 3, 2022] Morimitsu Kurino (Keio University)
Date & Time: 2022/03/03(Thu) 15:30-17:00
Title: Dual-Organ Markets: Coexistence of Living and Deceased Donors
Abstract: To overcome the worldwide shortage of deceased-donor organs, the medical community has developed various modalities of transplantation. For dual-organ transplantation, the shortage is serious as the modality requires two donors for a single patient. Lung transplantation, a representative example of dual-organ transplantation, is the only treatment for patients in the final stage of a chronic lung disease. Prior to April 2015, there were only two types of transplantation available: deceased-donor transplants and living-donor transplants. Ergin, Sönmez, and Ünver (2017) have proposed the idea of exchanging donors exclusively for living-donor lung transplantation. The new technology, called hybrid transplantation, is now available as evidenced as Dr. Oto and his team at Okayama University Hospital successfully transplanted a deceased lung and a lobe of live lung to one patient at the same time. As the modality itself reveals the importance of simultaneously operating the deceased- and living-donor markets, we study the market with both deceased- and living-donors. In particular, we point out that the hybrid transplantation opens up a new type of donor exchange. We investigate a mechanism of organizing transplants in terms of efficiency, fairness, and incentive-compatibility.
[Feb. 21, 2022] Ayumi Igarashi (National Institute of Informatics)
Date & Time: 2022/2/21(Mon) 10:25am-12:10
Title: Envy-free division of multi-layered cakes
Abstract: We study the problem of dividing a multi-layered cake among heterogeneous agents under non-overlapping constraints. This problem, recently proposed by Hosseini et al. (2020), captures several natural scenarios such as the allocation of multiple facilities over time where each agent can utilize at most one facility simultaneously, and the allocation of tasks over time where each agent can perform at most one task simultaneously. We establish the existence of an envy-free multi-division that is both non-overlapping and contiguous within each layered cake when the number n of agents is a prime power and the number m of layers is at most n, thus providing a positive partial answer to a recent open question. To achieve this, we employ a new approach based on a general fixed point theorem, originally proven by Volovikov (1996), and recently applied by Jojić, Panina, and Živaljević (2020) to the envy-free division problem of a cake. We further show that for a two-layered cake division among three agents with monotone preferences, an ε-approximate envy-free solution that is both non-overlapping and contiguous can be computed in logarithmic time of 1/ε.
[Feb. 17, 2022] Rakesh Vohra (University of Pennsylvania)
Date & Time: 2022/2/17(Thu) 9:00-10:45am
Title: ∆-Substitute Preferences and Equilibria with Indivisibilities
Abstract: An obstacle to the use of market mechanisms to allocate indivisible goods is the non-existence of competitive equilibria (CE). To surmount this Arrow and Hahn proposed the notion of social-approximate equilibria: a price vector and corresponding excess demands that are `small’. We identify social approximate equilibria where the excess demand, good-by-good, is bounded by a parameter Δ that depends on preferences only and not the size of the economy. The parameter Δ measures the degree of departure from substitute preferences. As a special case, we identify a class called geometric substitutes, that guarantees the existence of competitive equilibria in non-quasi-linear settings. It strictly generalizes prior conditions such as single improvement, no complementarities, gross substitutes and net substitutes. This is joint work with Thanh Nguyen.
[Jan. 13, 2022] Wolfgang Pesendorfer (Princeton University)
Date & Time: 2022/1/13(Thu) 9:00-10:30am
Title: Lindahl equilibrium as a collective choice rule
Abstract: A collective choice problem is a finite set of social alternatives and a finite set of economic agents with vNM utility functions. We associate a public goods economy with each collective choice problem and establish the existence and efficiency of (equal income) Lindahl equilibrium allocations. We interpret collective choice problems as cooperative bargaining problems and define a set-valued solution concept, the equitable solution (ES). We provide axioms that characterize ES and show that ES contains the Nash bargaining solution. Our main result shows that the set of ES payoffs is the same a the set of Lindahl equilibrium payoffs. We consider two applications: in the first, we show that in a large class of matching problems without transfers the set of Lindahl equilibrium payoffs is the same as the set of (equal income) Walrasian equilibrium payoffs. In our second application, we show that in any discrete exchange economy without transfers every Walrasian equilibrium payoff is a Lindahl equilibrium payoff of the corresponding collective choice market. Moreover, for any cooperative bargaining problem, it is possible to define a set of commodities so that the resulting economy’s utility possibility set is that bargaining problem and the resulting economy’s set of Walrasian equilibrium payoffs is the same as the set of Lindahl equilibrium payoffs of the corresponding collective choice market.
[Dec. 23, 2021] Zhen Lian (Cornell University)
Date & Time: 2021/12/23(Thu) 9:00-10:30am
Title: Autonomous Vehicle Market Design
Abstract: We develop an economic model of autonomous vehicle (AV) ride-hailing markets in which uncertain aggregate demand is served with a combination of a fixed fleet of AVs and an unlimited potential supply of human drivers (HVs). We analyze market outcomes under two dispatch platform designs (common platform vs. independent platforms) and two levels of AV competition (monopoly AV vs. competitive AV). A key result of our analysis is that the lower cost of AVs does not necessarily translate into lower prices; the price impact of AVs is ambiguous and depends critically on both the dispatch platform design and the level of competition. In the extreme case, we show if AVs and HVs operate on independent dispatch platforms and there is a monopoly AVs supplier, then prices are even higher than they are in a pure HV market. When AVs are introduced on a common dispatch platform, we show that whether the equilibrium price is reduced depends on the level of AV competition. If AVs are owned by a monopoly firm, then the equilibrium price is the same as in a pure HV market. In fact, the only market design that leads to unambiguously lower prices in all demand scenarios is when AVs and HVs operate on a common dispatch platform and the AV supply is competitive. Our results illustrate the critical role market design and competition plays in realizing potential welfare gains from AVs.
[Dec. 9, 2021] Jeremy Fox (Rice University)
Date & Time: 2021/12/9(Thu) 9:00-10:30am
Title: Measuring the Welfare Gains from Cardinal-Preference Pseudomarkets in School Choice
Abstract: We compare cardinal-preference and ordinal-preference mechanisms for assignment problems such as school choice, with a focus on a variant of the pseudomarket mechanism of Hylland and Zeckhauser (1979). We introduce and theoretically analyze a variant of the pseudomarket mechanism that has an equilibrium selection rule. We also introduce a computer algorithm to compute the implied stochastic assignment. We estimate cardinal preferences over schools using data on student submissions of rank ordered lists of schools in Seattle. Using these estimated preferences, we measure the welfare gains from using the pseudomarket mechanism instead of the ordinally-efficient probabilistic serial mechanism.
[Dec. 2, 2021] Aytek Erdil (University of Cambridge)
Date & Time: 2021/12/2(Thu) 17:00-18:30
Title: Widening Access with Smart Targets
Abstract: In the UK, universities advertise the degree majors (courses) they offer, and over 700,000 students apply directly to their chosen courses out of over 30,000 courses available. For each of their courses, universities have a target number of students to admit. Some universities also have a target number of disadvantaged students to admit in each course. Depending on student demand, each university adjusts these course-level targets over a long admissions calendar, and makes offers with the aim of fulfilling its aggregate (i.e., university-level) targets. We show that it is possible to reorganise this market with a centralised system which maintains universities’ flexibility to optimally adjust their targets. We design a strategy-proof mechanism that finds a stable matching in a market where students pursue their most preferred courses and universities aim to meet their targets with the best applicants possible.