Researcher:
Ünver, Utku

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Utku

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Ünver

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Ünver, Utku
Ünver, M. Utku

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2001 - 200982010 - 20182

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Researcher Of Publications: search.filters.isAuthorOfPublication.b238684a-6c67-4d83-8134-a1305d742d22

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Now showing 1 - 10 of 10
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    Kidney exchange
    (Massachusetts Institute of Technology (MIT) Press, 2004) Roth, Alvin E.; Department of Economics; Department of Economics; Sönmez, Tayfun; Ünver, Utku; Faculty Member; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; College of Administrative Sciences and Economics; N/A; N/A
    Most transplanted kidneys are from cadavers, but there are also many transplants from live donors. Recently, there have started to be kidney exchanges involving two donor-patient pairs such that each donor cannot give a kidney to the intended recipient because of immunological incompatibility, but each patient can receive a kidney from the other donor. Exchanges are also made in which a donor-patient pair makes a donation to someone waiting for a cadaver kidney, in return for the patient in the pair receiving high priority for a compatible cadaver kidney when one becomes available. There are stringent legal/ethical constraints on how exchanges can be conducted. We explore how larger scale exchanges of these kinds can be arranged efficiently and incentive compatibly, within existing constraints. The problem resembles some of the "housing" problems studied in the mechanism design literature for indivisible goods, with the novel feature that while live donor kidneys can be assigned simultaneously, cadaver kidneys cannot. In addition to studying the theoretical properties of the proposed kidney exchange, we present simulation results suggesting that the welfare gains from larger scale exchange would be substantial, both in increased number of feasible live donation transplants, and in improved match quality of transplanted kidneys.
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    Computerized matching algorithms to optimize matches and increase opportunities for live donor kidney exchange
    (2005) Saidman, SL; Roth, AE; Sönmez, T; Delmonico, FL; Department of Economics; Ünver, Utku; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; N/A
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    Asset price bubbles and crashes with near-zero-intelligence traders
    (Springer, 2006) Duffy, John; Department of Economics; Ünver, Utku; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; N/A
    We examine whether a simple agent-based model can generate asset price bubbles and crashes of the type observed in a series of laboratory asset market experiments beginning with the work of Smith, Suchanek and Williams (1988). We follow the methodology of Gode and Sunder (1993, 1997) and examine the outcomes that obtain when populations of zero-intelligence (ZI) budget constrained, artificial agents are placed in the various laboratory market environments that have given rise to price bubbles. We have to put more structure on the behavior of the ZI-agents in order to address features of the laboratory asset bubble environment. We show that our model of "near-zero-intelligence" traders, operating in the same double auction environments used in several different laboratory studies, generates asset price bubbles and crashes comparable to those observed in laboratory experiments and can also match other, more subtle features of the experimental data.
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    Credible group stability in many-to-many matching problems
    (Elsevier, 2006) Konishi, Hideo; Department of Economics; Ünver, Utku; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; N/A
    It is known that in two-sided many-to-many matching problems. pairwise-stable matchings may not be immune to group deviations. unlike in many-to-one matching problems (Blair. 1988). In this paper, we show that pairwise stability is equivalent to credible group stability when one side has responsive preferences and the other side has categorywise-responsive preferences. A credibly group-stable matching is immune to any "executable" group deviations with an appropriate definition of executability. Under the same preference restriction. we also show the equivalence between the set of pairwise-stable matchings and the set of matchings generated by coalition-proof Nash equilibria of an appropriately defined strategic-form game.
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    Backward unraveling over time: the evolution of strategic behavior in the entry level British medical labor markets
    (Elsevier Science Bv, 2001) Department of Economics; Ünver, Utku; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; N/A
    This paper studies an evolutionary programming technique, namely a genetic algorithm, to analyze how a population of decision-makers learn to coordinate the selection of an equilibrium or a social convention in a two-sided matching game with incomplete information. In the contexts of centralized and decentralized entry-level labor markets, evolution and adjustment paths of unraveling are explored using this technique in an environment inspired by the Kagel and Roth (2000. Quarterly Journal of Economics 115(1), 201-235) experimental study. As an interesting result, it is demonstrated that stability need not be required for the success of a matching mechanism under incomplete information in the long run.
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    On the survival of some unstable two-sided matching mechanisms
    (Physica-Verlag Gmbh & Co, 2005) Department of Economics; Ünver, Utku; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; N/A
    In the 1960s, three types of matching mechanisms were adopted in regional entry-level British medical labor markets to prevent unraveling of contract dates. One of these categories of matching mechanisms failed to prevent unraveling. Roth (1991) showed the instability of that failing category. One of the surviving categories was unstable as well, and Roth concluded that features of the environments of these mechanisms are responsible for their survival. However, Unver (2001) demonstrated that the successful yet unstable mechanisms performed better in preventing unraveling than the unsuccessful and unstable category in an artificial-adaptive-agent-based economy. In this paper, we conduct a human subject experiment in addition to short- and long-run artificial agent simulations to understand this puzzle. We find that both the unsuccessful and unstable mechanism and the successful and unstable mechanism perform poorly in preventing unraveling in the experiment and in short-run simulations, while long-run simulations support the previous Unver finding.
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    Room assignment-rent division: a market approach
    (Springer, 2004) Abdulkadiroğlu, Atila; Department of Economics; Department of Economics; Sönmez, Tayfun; Ünver, Utku; Faculty Member; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; College of Administrative Sciences and Economics; N/A; N/A
    A group of friends consider renting a house but they shall first agree on how to allocate its rooms and share the rent. We propose an auction mechanism for room assignment-rent division problems which mimics the market mechanism. Our auction mechanism is efficient, envy-free, individually-rational and it yields a non-negative price to each room whenever that is possible with envy-freeness.
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    House allocation with existing tenants: an equivalence
    (academic Press inc Elsevier Science, 2005) Department of Economics; Department of Economics; Sönmez, Tayfun; Ünver, Utku; Faculty Member; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; College of Administrative Sciences and Economics; N/A; N/A
    We analyze two mechanisms designed to eliminate inefficiencies in house allocation problems where there are both existing tenants and newcomers. the first mechanism chooses the unique core allocation of a "sister" exchange economy constructed by endowing each existing tenant with her current house and each newcomer with a random vacant house. the second mechanism chooses an ordering from a given distribution and determines the final outcome as follows: assign the agents the best available house one-at-a-time following their ordering in the queue and whenever an agent demands the house of an existing tenant who is still in the line, modify the queue by inserting the existing tenant at the top. Whenever a loop of existing tenants forms, Assign each of them the house she demands and proceed. We show that the first mechanism is equivalent to an extreme case of the second which favors the newcomers.
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    How (not) to integrate blood subtyping technology to kidney exchange
    (Elsevier, 2018) Department of Economics; Yılmaz, Özgür; Sönmez, Tayfun; Ünver, Utku; Faculty Member; Faculty Member; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638; N/A; N/A
    Even though kidney exchange became an important source of kidney transplants over the last decade with the introduction of market design techniques to organ transplantation, the shortage of kidneys for transplantation is greater than ever. Due to biological disadvantages, patient populations of blood types B/O are disproportionately hurt by this increasing shortage. The disadvantaged blood types are overrepresented among minorities in the US. In order to mitigate the disproportionate harm to these biologically disadvantaged groups, the UNOS reformed in 2014 the US deceased-donor kidney-allocation system, utilizing a technological advance in blood typing. The improved technology allows a certain fraction of blood type A kidneys, referred to as subtype A2 kidneys, to be transplanted to medically qualified patients of blood types B/O. The recent reform prioritizes subtype A2 deceased-donor kidneys for blood type B patients only. When restricted to the deceased-donor allocation system, this is merely a distributional reform with no adverse impact on the overall welfare of the patient population. In this paper we show that the current implementation of the reform has an unintended consequence, and it de facto extends the preferential allocation to kidney exchange as well. Ironically this "spillover" not only reduces the number of living-donor transplants for the overall patient population, but also for the biologically disadvantaged groups who are the intended beneficiaries of the reform. We show that minor variations of the current policy do not suffer from this unintended consequence, and we make two easy-to-implement, welfare-increasing policy recommendations.
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    Dual-donor organ exchange
    (Wiley, 2017) Ergin, Haluk; Department of Economics; Sönmez, Tayfun; Ünver, Utku; Faculty Member; Faculty Member; Department of Economics; College Of Administrative Sciences And Economics
    Owing to the worldwide shortage of deceased‐donor organs for transplantation, living donations have become a significant source of transplant organs. However, not all willing donors can donate to their intended recipients because of medical incompatibilities. These incompatibilities can be overcome by an exchange of donors between patients. For kidneys, such exchanges have become widespread in the last decade with the introduction of optimization and market design techniques to kidney exchange. A small but growing number of liver exchanges have also been conducted. Over the last two decades, a number of transplantation procedures emerged where organs from two living donors are transplanted to a single patient. Prominent examples include dual‐graft liver transplantation, lobar lung transplantation, and simultaneous liver‐kidney transplantation. Exchange, however, has been neither practiced nor introduced in this context. We introduce dual‐donor organ exchange as a novel transplantation modality, and through simulations show that living‐donor transplants can be significantly increased through such exchanges. We also provide a simple theoretical model for dual‐donor organ exchange and introduce optimal exchange mechanisms under various logistical constraints.