Sunday, July 14, 2024

Kidney exchange collaboration: Alliance for Paired Kidney Donation (APKD) and MedSleuth

 Here's a press release from MedSleuth about their collaboration with the Alliance for Paired Kidney Donation.

The Alliance for Paired Kidney Donation, MedSleuth Partner to Increase Access to Kidney Transplants  NEWS PROVIDED BY MedSleuth  

"SAN FRANCISCO and TOLEDO, Ohio, July 9, 2024 /PRNewswire/ -- The Alliance for Paired Kidney Donation (APKD), a global leader in paired kidney donation, and transplant software company MedSleuth announced today a U.S. partnership launched to increase access to lifesaving kidney transplants. The organizations have consolidated their two paired kidney donation software platforms into one program called Kidney Matchgrid, significantly expanding the pool for matching living kidney donors with transplant candidates nationwide.

"Today in the U.S., family, friends and other loved ones may offer the gift of living kidney donation to a person in need of a kidney transplant. While these willing donors are not always compatible with their intended recipient, this incompatibility doesn't have to mean the end of their journey. A process called paired donation allows incompatible donor-recipient pairs to be matched to each other. Paired donation can result in a kidney exchange, in which two incompatible donor-recipient pairs are matched to each other, or a kidney chain, in which a willing donor gives a kidney to a stranger and starts a domino effect of kidney donations.

"Before launching the new collaboration, MedSleuth and APKD operated independently to provide paired donation services and software to match living kidney donors with recipients. APKD focused on kidney exchanges between transplant centers, while MedSleuth focused on kidney exchanges within a single transplant center that was supported by software to improve living donor intake. With this new partnership, transplant centers now have access to a larger pool of patient data from which they can choose between internal, regional or national kidney exchanges.

"As a result, Kidney Matchgrid, a HIPAA-compliant, SOC 2 Type II certified software powered by a Nobel Prize-winning algorithm, better enables transplant centers to deliver both process efficiency and access to more transplants for their hard-to-match transplant candidates and living kidney donors.

"This partnership is an example of what can be achieved when organizations combine their strengths to better serve patients and medical teams across the transplant community," said Dr. Michael A. Rees, transplant surgeon and CEO of APKD. "Bringing together the transparent APKD matching process and the straightforward business practices of MedSleuth puts transplant centers first, giving them tools to make the best choices for the patients they serve."

"Transplant centers working with APKD and MedSleuth will upload information about their donor-recipient pairs and non-directed living donors to Kidney Matchgrid, from which transplant centers and APKD will perform match runs as frequently as desired. MedSleuth will support the partnership by overseeing the sales and marketing of Kidney Matchgrid for all participating transplant centers, allowing APKD to focus on helping transplant centers deliver kidney exchange and first-rate care to the living donors who make kidney exchange possible.

"This partnership enables us to channel our energy into delivering exceptional customer service and outcomes for transplant centers from the first contact and continuing with every match run coordinated by our partners at APKD," said Ben Nightingale, COO of MedSleuth. "We look forward to working with transplant centers nationwide to further living donor transplant effectiveness and save more lives."

"In addition to Kidney Matchgrid, the expanded transplant center network will continue receiving access to services and software provided independently by MedSleuth and APKD.

"APKD's best-in-class support services include concierge-level support for transplant coordinators, donor and recipient protection programs offering lost wage and travel reimbursements, and the APKD KidneyPledge™, which gives priority for chain-ending kidneys to non-directed donors and their family members should they need a kidney transplant in the future. MedSleuth will continue offering transplant centers its BREEZE software to simplify living donor intake, as well as solutions that streamline the transplant process from recipient evaluation through the donor and recipient follow up.

"More information about Kidney Matchgrid and the associated transplant center, patient and donor support services provided by the new partnership is available through APKD at and MedSleuth at

About the Alliance for Paired Kidney Donation

"The Alliance for Paired Kidney Donation (APKD) is a 501c3 with global reach that manages a kidney registry powered by a Nobel Prize-winning algorithm. APKD revolutionized kidney donation by performing the world's first non-simultaneous altruistic donor chain and the first international chain. APKD's commitment to innovation, research, education, technology and generosity allows it to fulfill its mission of saving lives by securing a living donor kidney transplant for every patient who needs one."

About MedSleuth 

MedSleuth seeks to expand access to transplantation by streamlining the transplant process. In addition to kidney paired donation, our BREEZE software platform simplifies candidate evaluation, optimizes waitlist management, and facilitates transplantation, with a focus on living donation. The patented, clinically validated platform collects relevant clinical and demographic data remotely, aiding participating transplant centers in their operations. For more information, visit"

Saturday, July 13, 2024

Covid vaccine boosters: promoting uptake is hard

 A recent study published in Nature shows that inexpensive nudges (to get Covid revaccinations) can have small but measurable effects (about 1 percentage point). The large scale study involving 18 coauthors planned to message 3,662,548 CVS Pharmacy patients  with reminders. The  experimental treatments included one message that also offered free rides to pharmacies. However that message did not further increase revaccinations.

Megastudy shows that reminders boost vaccination but adding free rides does not. by 

Katherine L. Milkman, Sean F. Ellis, Dena M. Gromet, Youngwoo Jung, Alex S. Luscher, Rayyan S. Mobarak, Madeline K. Paxson, Ramon A. Silvera Zumaran, Robert Kuan, Ron Berman, Neil A. Lewis Jr, John A. List, Mitesh S. Patel, Christophe Van den Bulte, Kevin G. Volpp, Maryann V. Beauvais, Jonathon K. Bellows, Cheryl A. Marandola & Angela L. Duckworth, Nature (2024)

Abstract: Encouraging routine COVID-19 vaccinations is likely to be a crucial policy challenge for decades to come. To avert hundreds of thousands of unnecessary hospitalizations and deaths, adoption will need to be higher than it was in the autumn of 2022 or 2023, when less than one-fifth of Americans received booster vaccines1,2. One approach to encouraging vaccination is to eliminate the friction of transportation hurdles. Previous research has shown that friction can hinder follow-through3 and that individuals who live farther from COVID-19 vaccination sites are less likely to get vaccinated4. However, the value of providing free round-trip transportation to vaccination sites is unknown. Here we show that offering people free round-trip Lyft rides to pharmacies has no benefit over and above sending them behaviourally informed text messages reminding them to get vaccinated. We determined this by running a megastudy with millions of CVS Pharmacy patients in the United States testing the effects of (1) free round-trip Lyft rides to CVS Pharmacies for vaccination appointments and (2) seven different sets of behaviourally informed vaccine reminder messages. Our results suggest that offering previously vaccinated individuals free rides to vaccination sites is not a good investment in the United States, contrary to the high expectations of both expert and lay forecasters. Instead, people in the United States should be sent behaviourally informed COVID-19 vaccination reminders, which increased the 30-day COVID-19 booster uptake by 21% (1.05 percentage points) and spilled over to increase 30-day influenza vaccinations by 8% (0.34 percentage points) in our megastudy. More rigorous testing of interventions to promote vaccination is needed to ensure that evidence-based solutions are deployed widely and that ineffective but intuitively appealing tools are discontinued.

Friday, July 12, 2024

Growth pains for legal marijuana, in Germany and New York

Transitioning from a thriving black market for marijuana to a regulated legal market isn't so easy.

The Guardian has the story from Germany, where so far clubs, but not shops, have been legalized:

Cannabis legalisation hampered by most German of substances: red tape. Activists say the rollout of laws permitting recreational use of the drug has been hampered by a ‘bureaucratic monster’  by Deborah Cole

"Joints now mingle openly with pints among fans watching the European football championship in host nation Germany, which in the spring became the first big EU country to legally allow personal recreational use of cannabis.

"That is, provided the fan is over 18, only carrying a small amount of the narcotic, not smoking in the stands of a stadium and not in possession of more than three plants at their officially registered home.


"The hotly disputed law passed by Olaf Scholz’s three-party coalition, which took effect in April, legalised cultivating up to three plants for private consumption, the possession of 50g (1.75oz) of cannabis at one time at home and 25g in public.


"A key phase began on 1 July with the establishment of registered cannabis clubs, which proponents say are vital to assuring the smooth path towards legal weed and supplanting the underworld street trade.


"In order to thwart drug tourism, members must have lived in Germany for six months, sign up to a club for a minimum of three months and have a clean criminal record for narcotics.

"Clubs are dependent on fee-paying members to start operating but are not allowed to advertise, said Marten Knopke of the Cannabis Social Club Leipzig, thus robbing them of a key source of capital needed to rent offices and land for growing purposes. Consumption on club premises is also verboten.

“We are subject to more restrictions than any alcohol company,” Knopke said, echoing a frequent complaint from the cannabis scene about drinking, which kills more than 60,000 people in Germany each year. “The government has also made it really difficult for us to stand up to the hidden [narcotics] market.”


“There are no shops where you can buy, meaning they [foreign tourists]" will end up buying something on the underground market, which is very dangerous in Berlin,” because of contaminated drugs and the role of the mafia in the trade, he said."


And here's the New York Times on New York:

The Real Problem With Legal WeedBy Charles Fain Lehman

"When New York legalized recreational marijuana in 2021, the future seemed bright. ...

"Three years later, things are not going to plan. Gov. Kathy Hochul has called New York’s legalization rollout “a disaster.” Mayor Eric Adams has spent months demanding that Albany fix the current system. “What happened?” The New Yorker recently asked in a feature on the collapse of the state’s marijuana “revolution.”


"There are around 140 recreational dispensaries operating statewide — about one for every 148,000 New Yorkers. Instead of shopping legally, New Yorkers tend to get their weed from the illegal shops that now blanket the state. Estimates suggest that there are anywhere from 2,000 to 8,000 in New York City alone, with uncounted more from Ithaca to Oneonta. Recent crackdowns have temporarily sealed more than 400 stores — only a small fraction of the total in the city.

"These shops undercut the legal stores, offering the same high at a fraction of the price. And they attract crime: There were 736 robbery complaints at unlicensed shops last year, according to the New York Police Department. Shootings are not uncommon, including the killing of a 36-year-old man captured on video last April.

"They also sell to teenagers, as The Times has reported. Teachers, prevention experts and pediatricians have raised the alarm about high schoolers smoking or vaping marijuana at school."

Thursday, July 11, 2024

"Discreteness is the better part of value" (Vince Crawford)

 One of the themes of the conference celebrating Vince Crawford (in anticipation of his 75th birthday) is how two of his early famous papers (Crawford and Knoer, 1981 and Kelso and Crawford, 1982)  helped unify matching theory and the theory of markets and competitive equilibria, and thus began to bring matching theory into mainstream economics.

Vince remarked that the unification of matching with the rest of economics also brought discrete (as opposed to continuous) mathematics into the mainstream of economic theory.

He said he had come to realize that "Discreteness is the better part of value."*

*This is of course a play on the common English language expression "Discretion is the better part of valor," which has an indirect and complicated Shakespearean connection, but in common usage is meant to give advice like "Look before you leap."

Wednesday, July 10, 2024

Great Market Hall in Budapest

 It's good to remember that before markets were digital, essentially all marketplaces were places.

Here I am trying to take in Budapest's Great Market Hall.

Tuesday, July 9, 2024

Child labor in soccer

Many laws seek to protect children from being exploited in the labor market, and there is widespread repugnance when it appears that such exploitation is taking place. (Think of the issues associated with children sewing soccer balls in Pakistan...)

But minors can also be professional athletes, and that turns out to be an issue in the Euro 2024 competitions, because star Spanish player Lamine Yamal is only 16 years old. (He was scouted at 6...)

Here's the story

Why Spain are Risking 30,000 Euro Fine by Playing Lamine Yamal at Euro 2024, by Robin Mumford 

"Yamal has started in each of Spain's group games so far, against Croatia and Italy, but a German law put Spain at risk of a €30,000 fine for his involvement in the game against Italy. That's because the German Youth Protection Act prohibits under-18s from working beyond a certain time - usually 8pm.

"Spain's first group game kicked off at 6pm local time, but their game against Italy started at 9pm. While there is an exceptional rule within the German law that authorises athletes to work until 11pm, the match finished very close to that time anyway, and post-match showers and interviews are also considered within the realms of labour, which means Spain may very well have met the conditions to be hit with a fine."

HT: Peter Biro


The Centre for Sport and Human Rights has a White Paper called

CHILD LABOUR IN SPORT. Protecting the Rights of Child Athletes

Monday, July 8, 2024

Top-trading-cycles for multiple-type housing markets by Di Feng , Bettina Klaus , and Flip Klijn

 On it's 50th anniversary, top trading cycles (TTC) is still well worth studying. Here's the latest:

Characterizing the typewise top-trading-cycles mechanism for multiple-type housing markets by Di Feng a, Bettina Klaus b, Flip Klijn , Games and Economic Behavior, Volume 146, July 2024, Pages 234-254


"We consider the generalization of the classical Shapley and Scarf housing market model (Shapley and Scarf, 1974) to so-called multiple-type housing markets (Moulin, 1995). Throughout the paper, we focus on strict preferences. When preferences are separable, the prominent solution for these markets is the typewise top-trading-cycles (tTTC) mechanism.

"We first show that for lexicographic preferences, a mechanism is unanimous (or onto), individually rational, strategy-proof, and non-bossy if and only if it is the tTTC mechanism. Second, we obtain a corresponding characterization for separable preferences. We obtain additional characterizations when replacing [strategy-proofness and non-bossiness] with self-enforcing group (or pairwise) strategy-proofness. Finally, we show that for strict preferences, there is no mechanism satisfying unanimity, individual rationality, and strategy-proofness.

"Our characterizations of the tTTC mechanism constitute the first characterizations of an extension of the prominent top-trading-cycles (TTC) mechanism to multiple-type housing markets."

Sunday, July 7, 2024

Mechanism and Institution Design in Budapest, in honor of Vince Crawford's 75th birthday: July 8-12 at Corvinus University

 Here's the high level program, and here's the detailed program.

I plan to speak on Wednesday about Ethical Issues in Market Design.

And here's the guest of honor: VINCENT P. CRAWFORD

Saturday, July 6, 2024

Morals and the limits of markets, WZB Berlin, 11 - 12 July 2024

 Here's a conference that looks interesting:

Morals and the limits of markets, WZB Berlin, 11 - 12 July 2024

Organizers:  Hande Erkut and Dorothea Kübler

"The workshop will focus on the limits of markets, the morality of decisions in markets, and paternalism. It will bring together scholars from different disciplines (mainly economics, political science, and philosophy) who are working on these topics. The workshop aims to foster discussions across disciplines on the ethical considerations surrounding market activities, repugnant markets, and the government’s role in regulating such markets."

Preliminary Program:Preliminary Program:

Thursday, July 11, 2024

9:00 – 9.30 Registration/ Workshop Opening

9:30 – 10.50 Sandro Ambühl (University of Zurich)  Interventionist Preferences and the Welfare State: The Case of In-Kind Nutrition Assistance

Tammy Harel Ben Shahar (University of Haifa), Lean Out: On the Morality of Participating in Positional Competitions

10:50 – 11:10 Coffee Break

11:10 – 12:30 Benjamin Sachs-Cobbe (University of St Andrews) Taking Jobs and Doing Harm

Colin Sullivan (Purdue University) Paternalistic Discrimination

12.30 – 13:20 Lunch

13:20 – 15:20 Hande Erkut (WZB), Repugnant Transactions: The Role of Agency and Severe Consequences

Erik Malmqvist (Univeristy of Gothenburg)  How Exploitation Harms

Constanze Binder (Erasmus University Rotterdam) Universities and Markets: New Challenges to Academic Freedom

15:20 – 15:50 Coffee Break

15.50 – 17:10 Robert Stüber (NYU Abu Dhabi) Why High Incentives Cause Repugnance: A Framed Field Experiment + Do Prices Erode Values

Aksel Sterri (Oslo Metropolitan University)  Bodily Justice

17:30 Visit to Neue Nationalgalerie

19:00 Conference Dinner

Friday, July 12, 2024

9.30 – 10:50 Axel Ockenfels (University of Cologne)  The Demand and Supply of Paternalism

Søren Flinch Midtgaard (Aarhus University) Reaction Qualifications and Paternalism

10:50 – 11.10 Coffee Break

11:10 – 12:30 Roberto Weber (University of Zurich) What Money Shouldn’t Buy: Aversion to Monetary Incentives for Health Behaviors

Amy Thompson (Oxford University) Defending a Moral Limit to Markets: Beyond a Singular Asymmetry Thesis

12.30 – 13:30 Lunch

13:30 – 15:30 Sili Zhang (LMU Munich)  What Money Can Buy: How Market Exchange Promotes Values

Peter Dietsch (University of Victoria)  The Centrifugal Nature of the Labour Market, Justice, and Public  Policy

Rahel Jaeggi (Humboldt University Berlin)  TBA

15:30 – 16:40 Coffee Break / Poster Session

Miguel Abellán (University Lüneburg) Timo Heinrich (TU Hamburg)

Victor Chung (University of Toronto) Iliana Melero (University of Zaragoza)

Denise Feigl (University of Regensburg) Brandon Long (University at Buffalo)

Ben Grodeck (University of Exeter) Reha Tuncer (LISER)

16:40 – 18:00 Nicola Lacetera (University of Toronto) Save and Let Die? Economic Factors and the Support of Medically Assisted Death

Stefan Gosepath (Frei University Berlin) Containment of the Market

19:00 Farewell Dinner

Friday, July 5, 2024

The Morality of Markets, by Mathias Dewatripont and Jean Tirole, in the JPE

 Are markets moral, immoral, or amoral?  Here's a new entry to that argument.

The Morality of Markets, by Mathias Dewatripont and Jean Tirole, Journal of Political Economy, online ahead of print.

Abstract: "Scholars and civil society have argued that competition erodes supplier morality. This paper establishes a robust irrelevance result, whereby intense market competition does not crowd out consequentialist ethics; it thereby issues a strong warning against the wholesale moral condemnation of markets and procompetitive institutions. Intense competition, while not altering the behavior of profitable suppliers, may, however, reduce the standards of highly ethical suppliers or not-for-profits, raising the potential need to protect the latter in the marketplace."

"The irrelevance result.—We ask: does the combination of unethical (or, more generally, UPI [unethical/present biased/influenceable]) consumers and of suppliers with consequentialist social preferences imply that moral behavior deteriorates under more intense competition? Our answer to this question is no. Indeed, under weak assumptions, the degree of competitive pressure is irrelevant to ethical behavior (moral choices are independent of demand functions) if prices are flexible.

"The intuition behind the irrelevance result goes as follows: when a supplier faces more intense competition (a more elastic demand), raising ethical behavior has a bigger negative impact on the supplier’s market share and is therefore costlier for the supplier; ceteris paribus, this makes suppliers cut ethical corners in reaction to the increase in competition, as indicated in the conventional wisdom. However, next to this first market share effect, there is a second reduced-stakes effect: a more intense competition reduces prices and markups, making supplier ethical concerns loom larger relative to material ones. We show that a sufficient condition for these two effects to exactly offset each other is that suppliers have consequentialist preferences and returns to scale are constant.

"The irrelevance result, which applies as well to ethical or indifferent consumers, is important not only because it sheds light on the validity of the widespread concern about markets expressed by the public opinion, social scientists, politicians, and religious leaders but also because it affects our stance vis-à-vis key competition-enhancing public policies, such as the opening of borders to free trade, competition policy, and the deregulation of industries. The irrelevance result is also in stark contrast with earlier theoretical results on the irrelevance of social preferences in highly competitive environments, in particular, with Dufwenberg et al. (2011) and Sobel (2015): in our case, the social preferences of suppliers and of consumers matter regardless of the competitive pressure, and it is the intensity of competition that is irrelevant. The difference is driven in particular by the fact that in their settings, one can affect others’ utilities only through one’s impact on their quantities traded or the market price, an impact that vanishes under perfect competition. In our setting, an individual may want to change her action just because it is objectionable to herself or others, even if this does not affect their ability to trade, a feature that is widespread in the real world. See the literature review for a detailed comparison."

Thursday, July 4, 2024

YingHua He 何 英华 has died.

 Yan Chen passes on the devastating news that YingHua He 何 英华 passed away on Tuesday night, after struggling with kidney cancer.

May his memory be a blessing.

He graduated from college in China in 2001, got an MA at Peking University, received his Ph.D. at Columbia in 2011, taught in Toulouse, and was an associate professor at Rice University when he died.

Here's his CV, and here is his Google Scholar page.  He did important work on market design, including on school choice and kidney exchange.

He was one of the pioneers of empirical market design, combining econometrics with matching theory. 

He had many friends, and I was lucky to be among them. Here's a photo I took of him giving a seminar at Stanford, when he was a visiting scholar in 2014-15

Yinghua He at Stanford, January 2015

Here are some of my blog posts on his work:

Wednesday, July 3, 2024

Kidney Exchange in KSA

 Here's a press release from King Faisal Specialist Hospital and Research Centre in Saudi Arabia:

KFSHRC Performs Over 5,000 Successful Kidney Transplants

Published: Jul 01, 2024

RIYADH, Saudi Arabia, July 01, 2024 (GLOBE NEWSWIRE) -- King Faisal Specialist Hospital and Research Centre (KFSHRC) has successfully performed 5,000 kidney transplants since the inception of its Transplant Program in 1981...


"Over the past decade, the program has experienced significant growth, with more than 3,000 transplants performed since 2010 and approximately 1,250 transplants in the last three years alone.

"Moreover, the establishment of the Kidney Paired Donation (KPD) program has significantly revolutionised the transplantation landscape by addressing the challenge of compatibility between patients and their donors. This program has helped patients who would otherwise face considerable obstacles in finding suitable matches. :

Tuesday, July 2, 2024

A proposal to assess public opinion in Europe on compensation for organ donors

 Here's a paper that proposes doing an experiment. Concerning compensation for organ donors. In Europe.  With the hope of influencing policy and reducing the shortage of transplants.  (A very worthy cause, that brings to mind Titian's painting of Sisyphus...)

Ambagtsheer, Frederike, Eline Bunnik, Liset HM Pengel, Marlies EJ Reinders, Julio J. Elias, Nicola Lacetera, and Mario Macis. "Public Opinions on Removing Disincentives and Introducing Incentives for Organ Donation: Proposing a European Research Agenda." Transplant International 37 (2024): 12483.

Abstract: The shortage of organs for transplantations is increasing in Europe as well as globally. Many initiatives to the organ shortage, such as opt-out systems for deceased donation and expanding living donation, have been insufficient to meet the rising demand for organs. In recurrent discussions on how to reduce organ shortage, financial incentives and removal of disincentives, have been proposed to stimulate living organ donation and increase the pool of available donor organs. It is important to understand not only the ethical acceptability of (dis)incentives for organ donation, but also its societal acceptance. In this review, we propose a research agenda to help guide future empirical studies on public preferences in Europe towards the removal of disincentives and introduction of incentives for organ donation. We first present a systematic literature review on public opinions concerning (financial) (dis)incentives for organ donation in European countries. Next, we describe the results of a randomized survey experiment conducted in the United States. This experiment is crucial because it suggests that societal support for incentivizing organ donation depends on the specific features and institutional design of the proposed incentive scheme. We conclude by proposing this experiment’s framework as a blueprint for European research on this topic.

Monday, July 1, 2024

Fairness, efficiency and strategy proofness in assigning indivisible objects: two new papers

 Here are two new papers on the burgeoning literature of matching people to scarce indivisible resources.

First, an experiment by Claudia CerroneYoan Hermstrüwer,  and Onur Kesten.

Claudia Cerrone, Yoan Hermstrüwer, Onur Kesten, School Choice with Consent: an Experiment, The Economic Journal, Volume 134, Issue 661, July 2024, Pages 1760–1805,

Abstract: Public school choice often yields student assignments that are neither fair nor efficient. The efficiency-adjusted deferred acceptance mechanism allows students to consent to waive priorities that have no effect on their assignments. A burgeoning recent literature places the efficiency-adjusted deferred acceptance mechanism at the centre of the trade-off between efficiency and fairness in school choice. Meanwhile, the Flemish Ministry of Education has taken the first steps to implement this algorithm in Belgium. We provide the first experimental evidence on the performance of the efficiency-adjusted deferred acceptance mechanism against the celebrated deferred acceptance mechanism. We find that both efficiency and truth-telling rates are higher under the efficiency-adjusted deferred acceptance mechanism than under the deferred acceptance mechanism, even though the efficiency-adjusted deferred acceptance mechanism is not strategy proof. When the priority waiver is enforced, efficiency further increases, while truth-telling rates decrease relative to variants of the efficiency-adjusted deferred acceptance mechanism where students can dodge the waiver. Our results challenge the importance of strategy proofness as a prerequisite for truth telling and portend a new trade-off between efficiency and vulnerability to preference manipulation.


And here's a theoretical paper by Xiang Han (韩翔)

Xiang Han, On the efficiency and fairness of deferred acceptance with single tie-breaking, Journal of Economic Theory, Volume 218, 2024, (

Abstract: As a random allocation rule for indivisible object allocation under weak priorities, deferred acceptance with single tie-breaking (DA-STB) is not ex-post constrained efficient. We first observe that it also fails to satisfy equal-top fairness, which requires that two agents be assigned their common top choice with equal probability if they have equal priority for it. Then, it is shown that DA-STB is ex-post constrained efficient, if and only if it is equal-top fair, if and only if the priority structure satisfies a certain acyclic condition. We further characterize the priority structures under which DA-STB is ex-post stable-and-efficient. Based on the characterized priority domains, and using a weak fairness notion called local envy-freeness, new theoretical support is provided for the use of this rule: for any priority structure, among the class of strategy-proof, ex-post stable, symmetric, and locally envy-free rules, each of the above desiderata—ex-post constrained efficiency, ex-post stability-and-efficiency, and equal-top fairness—can be achieved if and only if it can be achieved by DA-STB.