Showing posts with label papers. Show all posts
Showing posts with label papers. Show all posts

Monday, March 11, 2024

Global disparities in kidney disease and care

 Here's a report on the availability of treatment of kidney disease around the world.  If you are unlucky enough to have kidney failure (which is a top 10 cause of death), it's good to be in North America or Western Europe. Most countries (70%) have at least a minimal capacity to perform transplants. But if I read the map correctly, preemptive kidney transplants (i.e. transplants before dialysis, in map D below) are relatively common only in the U.S., Britain, and Norway. (And worldwide, a transplant costs less than two years of dialysis...)

Bello, A.K., Okpechi, I.G., Levin, A., Ye, F., Damster, S., Arruebo, S., Donner, J.A., Caskey, F.J., Cho, Y., Davids, M.R. and Davison, S.N., 2024. An update on the global disparities in kidney disease burden and care across world countries and regions. The Lancet Global Health, 12(3), pp.e382-e395.

"Background

"Since 2015, the International Society of Nephrology (ISN) Global Kidney Health Atlas (ISN-GKHA) has spearheaded multinational efforts to understand the status and capacity of countries to provide optimal kidney care, particularly in low-resource settings. In this iteration of the ISN-GKHA, we sought to extend previous findings by assessing availability, accessibility, quality, and affordability of medicines, kidney replacement therapy (KRT), and conservative kidney management (CKM).

...

"Findings

The literature review used information on prevalence of chronic kidney disease from 161 countries. The global median prevalence of chronic kidney disease was 9·5% (IQR 5·9–11·7) with the highest prevalence in Eastern and Central Europe (12·8%, 11·9–14·1). For the survey analysis, responses received covered 167 (87%) of 191 countries, representing 97·4% (7·700 billion of 7·903 billion) of the world population. Chronic haemodialysis was available in 162 (98%) of 165 countries, chronic peritoneal dialysis in 130 (79%), and kidney transplantation in 116 (70%). However, 121 (74%) of 164 countries were able to provide KRT to more than 50% of people with kidney failure. Children did not have access to haemodialysis in 12 (19%) of 62 countries, peritoneal dialysis in three (6%) countries, or kidney transplantation in three (6%) countries. CKM (non-dialysis management of people with kidney failure chosen through shared decision making) was available in 87 (53%) of 165 countries. The annual median costs of KRT were: US$19 380 per person for haemodialysis, $18 959 for peritoneal dialysis, and $26 903 for the first year of kidney transplantation. Overall, 74 (45%) of 166 countries allocated public funding to provide free haemodialysis at the point of delivery; use of this funding scheme increased with country income level. The median global prevalence of nephrologists was 11·8 per million population (IQR 1·8–24·8) with an 80-fold difference between low-income and high-income countries. Differing degrees of health workforce shortages were reported across regions and country income levels. A quarter of countries had a national chronic kidney disease-specific strategy (41 [25%] of 162) and chronic kidney disease was recognised as a health priority in 78 (48%) of 162 countries.



Figure 3 Worldwide incidence of general, deceased-donor, living-donor, and pre-emptive kidney transplantations (cases pmp per year) (A) Incidence of kidney transplantation. (B) Incidence of deceased-donor kidney transplantation. (C) Incidence of living-donor kidney transplantation. (D) Incidence of pre-emptive kidney transplantation. pmp=per million population

Even in the U.S., we aren't able to supply enough transplantable kidneys for everyone who needs one. Domestic kidney exchange helps fill some of the gap, but the gap, and the resulting number of premature deaths, is still huge.  It's enough to make you think about global kidney exchange...

Monday, March 4, 2024

50th anniversary of Shapley and Scarf (1974), and of the Journal of Mathematical Economics

Now available online is the first in what I understand will be a series of papers commemorating the 50th anniversary of the Journal of Mathematical Economics.  The paper by Shapley and Scarf appeared in volume 1, number 1. (Thayer Morrill and I will have a paper surveying the literature on the Top Trading Cycle (TTC) algorithm, which was introduced in that first paper.)

Housing markets since Shapley and Scarf by Mustafa Oğuz Afacan, Gaoji Hu, and Jiangtao Li, Journal of Mathematical Economics, Available online 1 March 2024, In Press, Journal Pre-proof, https://doi.org/10.1016/j.jmateco.2024.102967

Abstract: Shapley and Scarf (1974) appeared in the first issue of the Journal of Mathematical Economics, and is one of the journal’s most impactful publications. As we approach the remarkable milestone of the journal’s 50th anniversary (1974–2024), this article serves as a commemorative exploration of Shapley and Scarf (1974) and the extensive body of literature that follows it.

Monday, February 19, 2024

Kidney exchange in the U.S. from 2006-2021

 Here's an interesting look at the (ongoing) development of kidney exchange in the U.S

Temporal trends in kidney paired donation in the United States: 2006-2021 UNOS/OPTN database analysis, by Neetika Garg, Carrie Thiessen, Peter P. Reese, Matthew Cooper, Ruthanne Leishman, John Friedewald, Asif A. Sharfuddin, Angie G. Nishio Lucar, Darshana M. Dadhania, Vineeta Kumar, Amy D. Waterman, and Didier A. Mandelbrot, American Journal of Transplantation,  24, 1, P46-56, JANUARY 2024.

Abstract: Kidney paired donation (KPD) is a major innovation that is changing the landscape of kidney transplantation in the United States. We used the 2006-2021 United Network for Organ Sharing data to examine trends over time. KPD is increasing, with 1 in 5 living donor kidney transplants (LDKTs) in 2021 facilitated by KPD. The proportion of LDKT performed via KPD was comparable for non-Whites and Whites. An increasing proportion of KPD transplants are going to non-Whites. End-chain recipients are not identified in the database. To what extent these trends reflect how end-chain kidneys are allocated, as opposed to increase in living donation among minorities, remains unclear. Half the LDKT in 2021 in sensitized (panel reactive antibody ≥ 80%) and highly sensitized (panel reactive antibody ≥ 98%) groups occurred via KPD. Yet, the proportion of KPD transplants performed in sensitized recipients has declined since 2013, likely due to changes in the deceased donor allocation policies and newer KPD strategies such as compatible KPD. In 2021, 40% of the programs reported not performing any KPD transplants. Our study highlights the need for understanding barriers to pursuing and expanding KPD at the center level and the need for more detailed and accurate data collection at the national level.

"Kidney paired donation (KPD) is rapidly evolving and reshaping the landscape of living donor kidney transplantation (LDKT). Since the initial KPD transplants performed in the United States in 1999,1 the scope of KPD has expanded substantially. With the inclusion of nondirected donor,2 it has progressed from simple 2-way or multiple-way exchanges to nonsimultaneous kidney donor chains3 and, more recently, to advanced and voucher donations.4 Downstream from nondirected donors, chains often conclude with end-chain kidneys allocated to candidates on the deceased kidney donor waitlist without a living donor (LD).5 Historically used to overcome the barrier of ABO/human leukocyte antigens (HLA) incompatibility, KPD is being increasingly used by compatible donor-recipient pairs to obtain more suitable kidneys for the respective recipients.6 KPD programs can be single center or internal, regional, or national.7,8 The largest multicenter or national KPD programs in the United States are the National Kidney Registry,9 the Alliance for Paired Donation,10 the MatchGrid/Medsleuth program,11 and the program operated by the Organ Procurement and Transplantation Network (OPTN).12 While multicenter KPD often expands the pool of candidates to improve match possibilities, there are examples of very successful single-center programs."

Wednesday, February 14, 2024

Is Pay Transparency Good? (and for what, and for whom?) by Zoë Cullen

 Over the course of my academic career I have taught at a state university where salaries were public, a private university in which the department chair knew everyone's salary, another private university in which only the dean knew everyone's salary, and one in which I'm not sure exactly who knows what.  Here's a study (not focused on universities) focused on the larger effects of information about pay.

Is Pay Transparency Good?  by  Zoë Cullen, Journal of Economic Perspectives—Volume 38, Number 1—Winter 2024—Pages 153–180

"To understand the economics behind pay transparency, it is useful to categorize the types of pay transparency into three buckets: horizontal pay transparency, where coworkers at the same organization are informed of each other’s pay (the Lilly Ledbetter case); vertical transparency, where transparency extends to different layers of seniority within an organization; and cross-firm transparency, where workers and/or employers have access to the pay information of competing firms and organizations.

"Horizontal pay transparency gained traction politically because it could hold a bad actor accountable for “unfair” pay differences, as in the Lilly Ledbetter case. In specific situations where roles are clearly defined, this kind of pay transparency could be a starting point to identify discriminatory gaps in pay that are prohibited by the Equal Pay Act of 1963 and related laws. Research has shown that employers have responded to horizontal pay transparency by achieving equality through lower average pay overall.

...

"In contrast, vertical pay transparency and cross-firm pay transparency, while less equipped to hold specific organizations accountable for discrimination, have proven capable of raising productivity and raising wages by reducing information frictions in the labor market. Vertical pay transparency increases workers’ information about what they could earn if they were to be promoted. Because employees typically underestimate the steepness of financial rewards from promotion, vertical transparency raises expectations about potential earnings and has proven to boost effort and productivity in meritocratic environments. Cross-firm pay transparency, achieved through salary benchmarks like Glassdoor or salary ranges in job posts, informs prospective candidates about which employers pay more than others and leads applicants, especially those underpaid, to redirect their search toward higher paying firms and more favorable pay negotiations. Cross-firm pay transparency policies have also informed firms what their competitors are paying, increasing competition and putting upward pressure on wages. These pay transparency policies shine the light outward, away from coworkers under the same employer, toward vertical and cross-firm pay differences. 

...

"The pay transparency lever is, in the end, stunningly cheap and powerful. However, this comes with a warning. Among the lessons learned in the study of pay transparency is that more information is not always better. Thus, we describe an open field for pay transparency studies to identify where greater and more equal access to information can improve economic outcomes."

Tuesday, February 13, 2024

Incentives to take tests and get vaccinated

 As the pandemic phase of Covid-19 recedes, we can reflect on what we've learned about demand for tests and for vaccines.   Here's a paper from a year ago that I missed at the time  that discusses incentives and defaults.

Incentives and Defaults Can Increase COVID-19 Vaccine Intentions and Test Demand, by Marta Serra-Garcia and Nora Szech, Management Science, Vol. 69, No. 2, February 2023, Pages 723-1322, iii-iv

Abstract: Willingness to vaccinate and test are critical in the COVID-19 pandemic. We study the effects of two measures to increase the support of vaccination and testing: defaults and monetary compensations. Some organizations, such as restaurants, fire departments, hospitals, or governments in some countries, have used these measures. Yet there is the concern that compensations could erode intrinsic motivation and decrease vaccination intentions. We show that, in the early stages of the pandemic, both approaches, compensations and defaults, significantly increased COVID-19 test demand and vaccine intentions. Compensations for vaccines, however, need to be large enough because low compensations can backfire. We estimate heterogeneous treatment effects to document which groups are more likely to respond to these measures. The results show that defaults and avoidance of small compensations are especially important for individuals who are more skeptical of the vaccine, measured by their trust in the vaccine and their political views. Hence, both measures could be used in a targeted manner to achieve stronger results.

Sunday, January 7, 2024

Market Design for Surface Water , by Ferguson and Milgrom

 The potential market for surface water is a market in which any transfer of rights involves externalities affecting the water consumption of others.

Market Design for Surface Water  by Billy A. Ferguson & Paul Milgrom, NBER WORKING PAPER 32010, DOI 10.3386/w32010, December 2023

Abstract: Many proposed surface water transfers undergo a series of regulatory reviews designed to mitigate hydrological and economic externalities. While these reviews help limit externalities, they impose substantial transaction costs that also limit trade. To promote a well-functioning market for surface water in California, we describe how a new kind of water right and related regulatory practices can balance the trade-off between externalities and transaction costs, and how a Water Incentive Auction can incentivize a sufficient number of current rights holders to swap their old rights for the new ones. The Water Incentive Auction adapts lessons learned from the US government’s successful Broadcast Incentive Auction.

From the introduction:

"Why is there so little water trading in California despite the heterogeneous uses and huge price differences? The consensus among many economists studying water is that much of the problem lies in an archaic system of property rights, which was perhaps simple and clear enough to function well when California was first settled, but which is dysfunctional today. We will argue below that trading in traditional water rights creates externalities, so efficiency-enhancing changes in water allocations cannot be achieved by exhausting profitable bilateral trades. Rather, it requires a coordinated, multilateral effort. The next section on the Institutional Background provides a description of water rights and the externalities that can result from trade or from certain other decisions about uses. What is most novel in this paper comes after that: we analyze a mechanism that enacts a change in water rights that could lead to much more efficient trade.

Our analysis draws on lessons learned from the US Broadcast Incentive Auction in 2016-17, in which some rights to use radio spectrum for television broadcast were combined, converted, and subdivided into more flexible rights that were better suited for wireless broadband communications. This was accomplished using an auction procedure designed to provide an “incentive” for broadcasters to participate. As in that auction, participation in an analogous Water Rights Incentive Auction could be entirely voluntary, with current water users incentivized to participate because they could trade their existing rights for new, more flexible rights and possibly additional payments as determined by an auction. Just as the Broadcast Incentive Auction achieved its goals described in the National Broadband Plan even though many broadcasters chose not to sell their rights, a Water Incentive Auction could provide the substantial benefits of more flexible water rights even if many water users decline to participate. We describe some details of a possible Water Incentive Auctions in a later section of this paper."

Tuesday, December 19, 2023

Experimental economics, in Economics textbooks

 Here's a paper surveying introductory economics textbooks for statements (or lack of statements) about experimental economics, over fifty years. (That's just about the period  in which I've been doing experiments, since starting a long collaboration with the late Keith Murnighan  when we were both new assistant professors at the U of I in 1974, although in fact the article covers 1970-2019.)  Note from the figure below that textbooks lag not just the progress of science, but even its widespread recognition: Kahneman and Smith won their Nobel for experiments in 2002.

Changing perceptions about experimentation in economics: 50 years of evidence from principles textbooks, by Saileshsingh Gunessee and Tom Lane, Journal of Behavioral and Experimental Economics, Volume 107, December 2023.

"Abstract: Traditionally, economists often argued experiments play little or no useful role in our science. This paper employs a novel approach to track the historical evolution of this doctrine from 1970 to 2019, by constructing a dataset of 278 introductory economics textbooks. Quantitative and qualitative analysis shows that anti-experimental views were dominant and largely unchanged until 2000, but there has since been a trend towards textbooks making positive statements about experimentation. However, remarks that economic experiments are impossible have been (almost) eliminated only in the last decade, evidencing a sluggish change in perceptions. Supplementary interviews with key textbook authors confirm the historical trend of increased enthusiasm towards experiments, and suggest they are now accepted within the economic mainstream. Our findings hold important implications for how the empirical methodology of economics is understood by practitioners and students."

Based on the introductory chapter of each textbook, they "classified the book's position on economic experiments into one of five categories:

"1. The book's introduction states that doing experiments in economics is impossible, or that economic experiments are never done (hereafter, Impossible/Not Done).

"2. The book's introduction states that doing experiments in economics is difficult, or that economic experiments are rare (hereafter, Difficult/Rare).

"3. The book's introduction states that experiments are done in economics, or refers to economic experiments without mentioning their being rare or any difficulties involved in conducting them (hereafter, Done).

"4. The book's introduction does not mention experimentation in economics (hereafter, No Mention).9


"5. The book does not contain an introductory section (hereafter, No Intro)."



Monday, December 18, 2023

Algorithmic Mechanism Design With Investment, by Akbarpour, Kominers, Li, Li, and Milgrom,

 Mechanisms that are computationally complex may require approximation in implementation, which can change the incentive properties of the exact mechanism.   But progress can be made...

Algorithmic Mechanism Design With Investment, by Mohammad Akbarpour, Scott Duke Kominers, Kevin Michael Li, Shengwu Li, Paul Milgrom, Econometrica, First published: 07 December 2023, https://doi.org/10.3982/ECTA19559

Abstract: We study the investment incentives created by truthful mechanisms that allocate resources using approximation algorithms. Some approximation algorithms guarantee nearly 100% of the optimal welfare in the allocation problem but guarantee nothing when accounting for investment incentives. An algorithm's allocative and investment guarantees coincide if and only if its confirming negative externalities are sufficiently small. We introduce fast approximation algorithms for the knapsack problem that have no confirming negative externalities and guarantees close to 100% for both allocation and investment.

From the introduction:

"Approximation algorithms can be combined with pricing rules to produce truthful mechanisms, provided that the algorithm is “monotone” (Lavi, Mu'Alem, and Nisan (2003)). In this paper, we study the ex ante investment incentives created by such mechanisms.

"Suppose that one bidder can make a costly investment to change its value before participating in a truthful mechanism. As an initial result, we show that all truthful mechanisms using the same allocation algorithm entail the same investment incentives, so we can regard the investment incentives as properties of the algorithm itself.

"If an allocation algorithm exactly maximizes total welfare, then the corresponding truthful mechanism is a Vickrey–Clarke–Groves (VCG) mechanism. For VCG mechanisms, any single bidder's investment is profitable if and only it improves total welfare (Rogerson (1992)). In this respect, the VCG mechanisms are essentially unique. We find that a truthful mechanism aligns a bidder's investment incentives with welfare maximization only if there is some set of allocations such that, for generic valuation profiles, its allocation algorithm exactly maximizes welfare over that set. Many practical approximation algorithms do not have this structure and, as a result, lack efficient investment incentives.

"One might also hope that if an allocation algorithm approximately maximizes total welfare, then it generates approximately efficient investment incentives—but we show to the contrary that arbitrarily good approximations can have arbitrarily bad investment guarantees. To make this statement precise, we evaluate an algorithm's performance on any particular instance by the welfare it achieves divided by the maximum welfare. We refer to the worst-case ratio over all instances when values are exogenous as the allocative guarantee, and the worst-case ratio when one bidder's ex ante investment endogenously determines its value as the investment guarantee.1 (The investment guarantee measures welfare net of investment costs.)

"Because the investment guarantee is a worst case over instances and over investment technologies, it is never more than the allocative guarantee. We characterize the algorithms for which the allocative and investment guarantees are equal, and apply those results to evaluate and improve upon standard approximation algorithms."

Monday, December 11, 2023

Market Design and Maintenance (new NBER working paper, from a conference)

This paper began as a presentation at the NBER conference on New Directions in Market Design, in the Spring of 2023

 Market Design and Maintenance by Alvin E. Roth.  NBER WORKING PAPER 31947
DOI 10.3386/w31947, ISSUE DATE December 2023

Abstract: Because no marketplace operates in isolation from the larger world, marketplace designs may need to adapt to changes in the larger environments. I discuss such changes in connection with the labor markets for new doctors, new Ph.D. economists, and for kidney exchange transplants. But while practical market design presents a host of challenges, it also offers many rewards. Among the rewards to market designers themselves is the opportunity to become intimately familiar with markets that shape the lives and careers of their participants.

************
There will eventually be a conference volume published by U. Chicago Press, and some of the papers are already online, and slides and  videos from the conference are here.

Thursday, November 16, 2023

Top trading cycles 'respect improvements' by rewarding agents whose endowments become more desirable

 Here's a wide-ranging paper that explores the way the Top Tradinig Cycles (TTC) algorithm 'respects improvements' by rewarding an agent whose endowment becomes more desirable.

Biró, Péter, Flip Klijn, Xenia Klimentova, and Ana Viana. "Shapley–Scarf Housing Markets: Respecting Improvement, Integer Programming, and Kidney Exchange." Mathematics of Operations Research (2023).

"Abstract: In a housing market of Shapley and Scarf, each agent is endowed with one indivisible object and has preferences over all objects. An allocation of the objects is in the (strong) core if there exists no (weakly) blocking coalition. We show that, for strict preferences, the unique strong core allocation “respects improvement”—if an agent’s object becomes more desirable for some other agents, then the agent’s allotment in the unique strong core allocation weakly improves. We extend this result to weak preferences for both the strong core (conditional on nonemptiness) and the set of competitive allocations (using probabilistic allocations and stochastic dominance). There are no counterparts of the latter two results in the two-sided matching literature. We provide examples to show how our results break down when there is a bound on the length of exchange cycles. Respecting improvements is an important property for applications of the housing markets model, such as kidney exchange: it incentivizes each patient to bring the best possible set of donors to the market. We conduct computer simulations using markets that resemble the pools of kidney exchange programs. We compare the game-theoretical solutions with current techniques (maximum size and maximum weight allocations) in terms of violations of the respecting improvement property. We find that game-theoretical solutions fare much better at respecting improvements even when exchange cycles are bounded, and they do so at a low efficiency cost. As a stepping stone for our simulations, we provide novel integer programming formulations for computing core, competitive, and strong core allocations."

Here is their literature review:

"The nonemptiness of the core is proved in Shapley and Scarf [47] by showing the balancedness of the corresponding nontransferable utility game and also in a constructive way by showing that David Gale’s famous top trading cycles (TTC) algorithm always yields competitive allocations. Roth and Postlewaite [40] later show that, for strict preferences, the TTC results in the unique strong core allocation, which coincides with the unique competitive allocation in this case. However, if preferences are not strict (i.e., ties are present), the strong core can be empty or contain more than one allocation, but the TTC still produces all competitive allocations. Wako [50] shows that the strong core is always a subset of the set of competitive allocations. Quint and Wako [39] provide an efficient algorithm for finding a strong core allocation whenever there exists one. Their work is further generalized and simplified by Cechlárová and Fleiner [19], who use graph models. Wako [52] shows that the set of competitive allocations coincides with the core based on an antisymmetric weak domination concept, which we refer to as Wako-core in this paper. This equivalence is key for our extension of the definition of competitive allocations to the case of bounded exchange cycles.

1.2.2. Respecting Improvement.

"For Gale and Shapley’s [23] college admissions model, Balinski and Sönmez [11] prove that SOSM respects improvement of student’s quality. Kominers [29] generalizes this result to more general settings. Balinski and Sönmez [11] also show that SOSM is the unique stable mechanism that respects improvement of student quality. Abdulkadiroğlu and Sönmez [3] propose and discuss the use of TTC in a model of school choice, which is closely related to the college admissions model. Abdulkadiroğlu and Che [2] state and Hatfield et al. [25] formally prove that the TTC mechanism respects improvement of student quality.

"Hatfield et al. [25] also focus on the other side of the market and study the existence of mechanisms that respect improvement of a college’s quality. The fact that colleges can match with multiple students leads to a strong impossibility result: they prove that there is no stable or Pareto-efficient mechanism that respects improvement of a college’s quality. In particular, the (Pareto-efficient) TTC mechanism does not respect improvement of a college’s quality.

"In the context of KEPs with pairwise exchanges, the incentives for bringing an additional donor to the exchange pool was first studied by Roth et al. [42]. In the model of housing markets their donor-monotonicity property boils down to the respecting improvement property. They show that so-called priority mechanisms are donor-monotonic if each agent’s preferences are dichotomous, that is, the agent is indifferent between all acceptable donors. However, if agents have nondichotomous preferences, then any mechanism that maximizes the number of pairwise exchanges (so, in particular, any priority mechanism) does not respect improvement. This can be easily seen by means of Example 4 in Section 3.3.

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See also

The core of housing markets from an agent’s perspective: Is it worth sprucing up your home?  by Ildiko Schlotter, , Peter Biro, and Tamas Fleiner

Abstract. We study housing markets as introduced by Shapley and Scarf (1974). We investigate the computational complexity of various questions regarding the situation of an agent a in a housing market Hwe show that it is NP-hard to find an allocation in the core of H where (i) a receives a certain house, (ii) a does not receive a certain house, or (iii) a receives a house other than her own. We prove that the core of housing markets respects improvement in the following sense: given an allocation in the core of H where agent a receives a house h, if the value of the house owned by a increases, then the resulting housing market admits an allocation in its core in which a receives either h or a house that a prefers to h; moreover, such an allocation can be found efficiently. We further show an analogous result in the Stable Roommates setting by proving that stable matchings in a one-sided market also respect improvement.


Friday, September 15, 2023

Regulating research and research misconduct

 Peer review is a clunky process that often misfires, but it helps to keep up the quality of published research. Much the same can be said about procedures for investigating allegations of research misconduct: they help clean up the research record, but they can also harm the innocent (particularly when accusations may be weaponized against competitors).*

Nature has the story of an investigator whose research was put on hold for four years before the accusations against him were dismissed after a lengthy investigtion:

‘Gagged and blindsided’: how an allegation of research misconduct affected our lab. Bioengineer Ram Sasisekharan describes the impact of a four-year investigation by the Massachusetts Institute of Technology, which ultimately cleared him.  by Anne Gulland

"In May 2019, a phone call to Ram Sasisekharan from a reporter at The Wall Street Journal triggered a chain of events that stalled the bioengineer’s research, decimated his laboratory group and, he says, left him unable to help find treatments for emerging infectious diseases during a global pandemic.

"The journalist had rung Sasisekharan, who works at the Massachusetts Institute of Technology (MIT) in Cambridge, for his comment on an article in the journal mAbs that had been published a few days previously1. The article alleged that Sasisekharan and his co-authors had “an intent to mislead as to the level of originality and significance of the published work”.

...

"At first, Sasisekharan assumed this was a storm he could weather by providing scientific evidence to refute the allegation, which related to two papers he had published with collaborators, in the Proceedings of the National Academy of Sciences (PNAS)2 and Cell Host & Microbe3. But then, MIT received a formal complaint of research misconduct against Sasisekharan, triggering an internal investigation that took more than three years and only concluded this March, when he was exonerated.

...

"Although the accusation had a huge impact on him in terms of his reputation, it was even harder for his staff, he says. “A lab is like a family — you have undergraduate and graduate students, as well as postdocs. The culture of a group and how we communicate is what makes it vibrant, and it was terrible to see how the lab suffered as a consequence of these very public allegations.” He adds: “You get really isolated, you stop being invited to things. There was this dark cloud hanging over us because we just couldn’t talk about it openly or defend ourselves.”

#######

*the postscript of this previous post comes to mind.

Monday, September 4, 2023

Covid medication: allocation, information, hesitancy, and uptake: what are some things we have learned?

 I've posted before about how informational advertising about vaccine availability and safety seems to have had a positive effect on vaccination rates among disadvantaged populations. There was particular concern in the U.S. at one point that Black people were less likely to receive vaccines and other medications than other Americans.

Today's post collects several papers about the effect of randomly allocating invitations for temporarily scarce Covid medications, while giving members of disadvantaged groups a higher probability of receiving an invitation.  Included will be an editorial warning us that we shouldn't be satisfied to judge the outcome of a market design by its intended outcome ("Moving Beyond Intent and Realizing Health Equity").

There are market design lessons in these last few years of Covid experience that I hope will help make the responses to future pandemics more effective. Not least of these is that the allocation of public health  and medical resources turns out to be quite different from  the allocation of other kinds of resources, in many important ways that reflect the broader economic and social environments in which different kinds of allocation takes place.

###

Here's a paper in the most recent issue of JAMA Health Forum, by a team that includes both medical professionals and market designers.

Weighted Lottery to Equitably Allocate Scarce Supply of COVID-19 Monoclonal Antibody , by Erin K. McCreary, PharmD1; Utibe R. Essien, MD, MPH2,3; Chung-Chou H. Chang, PhD4,5; Rachel A. Butler, MHA, MPH6; Parag Pathak, PhD7; Tayfun Sönmez, PhD8; M. Utku Ünver, PhD8; Ashley Steiner, BS9; Maddie Chrisman, PT, DPT10; Derek C. Angus, MD, MPH11; Douglas B. White, MD, MAS11, JAMA Health Forum. 2023;4(9):e232774. Sept. 1, doi:10.1001/jamahealthforum.2023.2774 

"Objective  To describe the development and use of a weighted lottery to allocate a scarce supply of tixagevimab with cilgavimab as preexposure prophylaxis to COVID-19 for immunocompromised individuals and examine whether this promoted equitable allocation to disadvantaged populations.

"Design, Setting, and Participants  This quality improvement study analyzed a weighted lottery process from December 8, 2021, to February 23, 2022, that assigned twice the odds of drug allocation of 450 tixagevimab with cilgavimab doses to individuals residing in highly disadvantaged neighborhoods according to the US Area Deprivation Index (ADI) in a 35-hospital system in Pennsylvania, New York, and Maryland. In all, 10 834 individuals were eligible for the lottery. Weighted lottery results were compared with 10 000 simulated unweighted lotteries in the same cohort performed after drug allocation occurred.

"Main Outcomes:  Proportion of individuals from disadvantaged neighborhoods and Black individuals who were allocated and received tixagevimab with cilgavimab.

"Results:  Of the 10 834 eligible individuals, 1800 (16.6%) were from disadvantaged neighborhoods and 767 (7.1%) were Black. Mean (SD) age was 62.9 (18.8) years, and 5471 (50.5%) were women. A higher proportion of individuals from disadvantaged neighborhoods was allocated the drug in the ADI-weighted lottery compared with the unweighted lottery (29.1% vs 16.6%; P < .001). The proportion of Black individuals allocated the drug was greater in the weighted lottery (9.1% vs 7.1%; P < .001). Among the 450 individuals allocated tixagevimab with cilgavimab in the ADI-weighted lottery, similar proportions of individuals from disadvantaged neighborhoods accepted the allocation and received the drug compared with those from other neighborhoods (27.5% vs 27.9%; P = .93). However, Black individuals allocated the drug were less likely to receive it compared with White individuals (3 of 41 [7.3%] vs 118 of 402 [29.4%]; P = .003).

...

"Conclusions and Relevance:  The findings of this quality improvement study suggest an ADI-weighted lottery process to allocate scarce resources is feasible in a large health system and resulted in more drug allocation to and receipt of drug by individuals who reside in disadvantaged neighborhoods. Although the ADI-weighted lottery also resulted in more drug allocation to Black individuals compared with an unweighted process, they were less likely to accept allocation and receive it compared with White individuals. Further strategies are needed to ensure that Black individuals receive scarce medications allocated."

...

"The lottery was repeated over several weeks, but we chose to examine only the first assignment. The interpretation of later rounds is problematic because eventually all individuals were offered tixagevimab with cilgavimab. By focusing on the first draw, we can specifically evaluate whether the intent of the lottery was met."

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Closely related reports:

White, D.B., McCreary, E.K., Chang, C.C.H., Schmidhofer, M., Bariola, J.R., Jonassaint, N.N., Persad, G., Truog, R.D., Pathak, P., Sonmez, T. and Unver, M.U., 2022. A multicenter weighted lottery to equitably allocate scarce COVID-19 therapeutics. American Journal of Respiratory and Critical Care Medicine, 206(4), pp.503-506.

Rubin, E., Dryden-Peterson, S.L., Hammond, S.P., Lennes, I., Letourneau, A.R., Pathak, P., Sonmez, T. and Ünver, M.U., 2021. A novel approach to equitable distribution of scarce therapeutics: institutional experience implementing a reserve system for allocation of COVID-19 monoclonal antibodies. Chest, 160(6), pp.2324-2331.*

White, D.B. and Angus, D.C., 2020. A proposed lottery system to allocate scarce COVID-19 medications: promoting fairness and generating knowledge. Jama, 324(4), pp.329-330.

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And here's an editorial in the same issue of JAMA Health Forum as the most recent article, pointing out that less-disadvantaged patients among those living in census blocks identified as disadvantaged (in particular  commercially insured and White patients) were much more likely to receive the treatment:

Moving Beyond Intent and Realizing Health Equity, by Atheendar S. Venkataramani, MD, PhD, Invited Commentary, September 1, 2023, JAMA Health Forum. 2023;4(9):e232525. doi:10.1001/jamahealthforum.2023.2525

"In a study published in this issue of JAMA Health Forum, McCreary and colleagues3 report on a landmark effort at the University of Pittsburgh Medical Center (UPMC) to distribute equitably a scarce monoclonal antibody resource, tixagevimab with cilgavimab, for COVID-19 preexposure prophylaxis in immunocompromised individuals. In December 2021, UPMC received an allotment of 450 doses of tixagevimab with cilgavimab from the Pennsylvania Department of Health to cover a large health system with 35 hospitals and 800 outpatient facilities through February 2022. In an ex ante effort to mitigate health disparities and respond to guidance from the Commonwealth of Pennsylvania to allocate scarce resources in a manner that accounts for multiple ethical objectives, UPMC convened an advisory group of clinicians, community stakeholders, and experts in community outreach.

...

"The lottery was constructed using the Area Deprivation Index (ADI) to ensure that patients in highly disadvantaged neighborhoods had an equal opportunity to access tixagevimab with cilgavimab. Patients living in neighborhoods with ADIs above a specific cutoff that has been shown to best target less affluent, rural, and Black patients received 2 entries in the lottery, compared with 1 entry for patients in more advantaged neighborhoods. In their study, McCreary and colleagues3 found that this process resulted in equitable access: similar proportions of individuals in more advantaged and more disadvantaged neighborhoods (about 28% in each group) received tixagevimab with cilgavimab during the study period, although Black patients who were allocated the drug in the lottery were significantly less likely to receive it compared with White patients (7.3% vs 29.4%).

...

"Having identified its patient population, UPMC required only patient addresses as well as publicly available data on ADIs to implement the lottery intervention. The ADIs are defined at the census block group level, which include about 1000 residents on average. Thus, UPMC was able to achieve equitable opportunity to access tixagevimab with cilgavimab across small localities with very different socioeconomic profiles.

...

On the other hand, higher-resolution data that specifically measure the types of intersecting, reinforcing, and cumulative disadvantages faced by historically marginalized groups5 may be needed to achieve equitable outcomes across other dimensions, such as race and ethnicity. Within census blocks, patients assigned the same ADI levels but who may have faced relatively fewer structural barriers compared with Black patients or patients receiving Medicaid—namely, commercially insured and White patients—were more likely to access tixagevimab with cilgavimab conditional on being allocated to receive it in the lottery

...

"The lower rates of drug receipt among Black patients also underscores the importance of complementary investments and operational decisions to address additional structural barriers to accessing medical technology.

...

"The study by McCreary and colleagues3 represents the type of courageous and rigorous work that is needed to chart a path forward in determining how best to bridge the access gap for leading-edge medical technology. Future work would benefit from the same type of clarity demonstrated in this study by including clear definitions for how equity should be operationalized, attempting to address fragmentation between clinical services and services that address social drivers of health, aligning incentives, and addressing historical barriers that have made it difficult to achieve health equity."

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*Earlier:

Saturday, August 14, 2021


Wednesday, August 30, 2023

Minimal envy mechanisms, by Julien Combe

 Here's an article I missed when it came out online:

Reallocation with priorities and minimal envy mechanisms, by Julien Combe, Economic Theory volume 76, 551–584 (2023)

"Abstract: We investigate the problem of reallocation with priorities where one has to assign objects or positions to individuals. Agents can have an initial ownership over an object. Each object has a priority ordering over the agents. In this framework, there is no mechanism that is both individually rational (IR) and stable, i.e. has no blocking pairs. Given this impossibility, an alternative approach is to compare mechanisms based on the blocking pairs they generate. A mechanism has minimal envy within a set of mechanisms if there is no other mechanism in the set that always leads to a set of blocking pairs included in the one of the former mechanism. Our main result shows that the modified Deferred Acceptance mechanism (Guillen and Kesten in Int Econ Rev 53(3):1027–1046, 2012), is a minimal envy mechanism in the set of IR and strategy-proof mechanisms. We also show that an extension of the Top Trading Cycle (Karakaya et al. in J Econ Theory 184:104948, 2019) mechanism is a minimal envy mechanism in the set of IR, strategy-proof and Pareto-efficient mechanisms. These two results extend the existing ones in school choice."

Friday, August 11, 2023

Freezing (and then carefully warming) donor organs breaks the organ transplant time barrier (for rats, for the time being)

 Here's a note in Nature Reviews Nephrology pointing out the longer term promise of the recent successful freezing, thawing, and transplantation of rat kidneys.

Cryopreservation breaks the organ transplant time barrier by Marlon J. A. de Haan & Ton J. Rabelink, in Nature Reviews Nephrology (2023)

"The pressing issue of organ shortages for transplantation is fuelled by the rising incidence of kidney failure and the declining quality of organs from an ageing donor pool. However, the main bottleneck in organ transplantation is time; indeed, the current clinical standard for kidney preservation necessitates immediate transplantation following organ recovery1. This urgency often results in suboptimal matches between donors and recipients. Cryopreservation has emerged as a potential solution to this challenge. Such an approach would enable organs to be preserved in a suspended state for extended periods and ready for transplantation on demand. The prospect of long-term banking of cryopreserved organs holds promise for transforming organ transplantation into an elective procedure, thereby enhancing donor–recipient matching, improving equity in access, optimizing patient preparation, refining transplant tolerance protocols, increasing organ utilization and improving graft and patient survival. However, even though cryopreservation has successfully been used to store human embryos, extending the process to preserve whole organs has remained a scientific aspiration — until now. A study by Han et al. introduces an approach to cryopreservation that seemingly extends the shelf life of organs indefinitely2."

...

"By rapidly cooling rat kidneys to –150°C, Han et al. were able to halt the biological clock of the organs, effectively inducing a glass-like state — a process known as vitrification2 (Fig. 1). Specifically, the researchers perfused a cocktail of cryoprotective agents (CPAs) and iron oxide nanoparticles into the organ’s vasculature, which they followed by rapid cooling to ultralow temperatures to achieve a state of vitrification. This vitrified kidney, with its hard, smooth, glasslike appearance, was then transferred to a –150°C freezer for long-term banking. When these kidneys were later rewarmed and transplanted into nephrectomized recipients, they regained life-sustaining renal function. The rewarming stage poses more challenges to the process of cryopreservation: it requires both speed to avoid ice formation during devitrification and uniformity to prevent thermal stresses and mechanical cracks. Here, the iron oxide nanoparticles had a crucial role. Placing the vitrified kidney in a coil that generates electromagnetic fields activates these nanoparticles, generating heat. This innovative approach enabled rapid rewarming at an impressive rate of approximately 72 °C per minute throughout the entire organ, ensuring uniform warming rather than limiting warming to the organs’ surface. This ground-breaking milestone marks an extraordinary achievement in ‘reviving’ a complex organ like the kidney and is the culmination of decades of research into methods to prevent the destructive formation of ice during the cooling process, minimize toxicity from CPAs, and enable fast and uniform rewarming3.



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Recently:

Wednesday, June 28, 2023

Wednesday, June 28, 2023

Freezing, thawing and transplanting a rat kidney: a first step towards organ banking

 A kidney has been frozen, thawed, and successfully transplanted, into a rat.  Maybe we'll live to see organ banking...

Vitrification and nanowarming enable long-term organ cryopreservation and life-sustaining kidney transplantation in a rat model   by Zonghu Han, Joseph Sushil Rao, Lakshya Gangwar, Bat-Erdene Namsrai, Jacqueline L. Pasek-Allen, Michael L. Etheridge, Susan M. Wolf, Timothy L. Pruett, John C. Bischof & Erik B. Finger, Nature Communications volume 14, Article number: 3407 (2023) 

Abstract: Banking cryopreserved organs could transform transplantation into a planned procedure that more equitably reaches patients regardless of geographical and time constraints. Previous organ cryopreservation attempts have failed primarily due to ice formation, but a promising alternative is vitrification, or the rapid cooling of organs to a stable, ice-free, glass-like state. However, rewarming of vitrified organs can similarly fail due to ice crystallization if rewarming is too slow or cracking from thermal stress if rewarming is not uniform. Here we use “nanowarming,” which employs alternating magnetic fields to heat nanoparticles within the organ vasculature, to achieve both rapid and uniform warming, after which the nanoparticles are removed by perfusion. We show that vitrified kidneys can be cryogenically stored (up to 100 days) and successfully recovered by nanowarming to allow transplantation and restore life-sustaining full renal function in nephrectomized recipients in a male rat model. Scaling this technology may one day enable organ banking for improved transplantation.

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Earlier:

Monday, June 12, 2017

Organ preservation could bring big changes to transplantation

Transplantation would be a lot less hectic if organs could be preserved. Here's a 42-author paper (the biggest coauthorship I've been involved in) that discusses some of the possibilities.

The promise of organ and tissue preservation to transform medicine 
 Sebastian Giwa, Jedediah K Lewis, Luis Alvarez, Robert Langer, Alvin E Roth, George M Church, James F Markmann, David H Sachs, Anil Chandraker, Jason A Wertheim, Martine Rothblatt, Edward S Boyden, Elling Eidbo, W P Andrew Lee, Bohdan Pomahac, Gerald Brandacher, David M Weinstock, Gloria Elliott, David Nelson, Jason P Acker, Korkut Uygun, Boris Schmalz, Brad P Weegman, Alessandro Tocchio, Greg M Fahy, Kenneth B Storey, Boris Rubinsky, John Bischof, Janet A W Elliott, Teresa K Woodruff, G John Morris, Utkan Demirci, Kelvin G M Brockbank, Erik J Woods, Robert N Ben, John G Baust, Dayong Gao, Barry Fuller, Yoed Rabin, David C Kravitz, Michael J Taylor & Mehmet Toner

Tuesday, June 20, 2023

Equilibrium effects of pay transparency--by Zoe Cullen and Bobby Pakzad-Hurson

 From the current issue of Econometrica, the lowdown on pay transparency:

Cullen, Zoe B., and Bobak Pakzad‐Hurson. "Equilibrium effects of pay transparency." Econometrica 91, no. 3 (2023): 765-802.

"Abstract: The discourse around pay transparency has focused on partial equilibrium effects: how workers rectify pay inequities through informed renegotiation. We investigate how employers respond in equilibrium. We study a model of bargaining under two-sided incomplete information. Our model predicts that transparency reduces the individual bargaining power of workers, leading to lower average wages. A key insight is that employers credibly refuse to pay high wages to any one worker to avoid costly renegotiations with others. When workers have low individual bargaining power, pay transparency has a muted effect. We test our model with an event-study analysis of U.S. state-level laws protecting the right of private sector workers to communicate salary information with their coworkers. Consistent with our theoretical predictions, transparency laws empirically lead wages to decline by approximately 2%, and wage declines are smallest in magnitude when workers have low individual bargaining power."

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Earlier:

Wednesday, March 29, 2023

Thursday, June 15, 2023

School choice and related matching algorithms in France, by Vincent Iehlé and Julien Jacqmin

Here's a recent paper that looks at the assignment of students to some of France's Grandes Ecoles, and draws some conclusions about the preferences for those schools.

SIGEM : analyse de la procédure d’affectation dans les grandes écoles de management,, Vincent Iehlé, Julien Jacqmin, Dans Revue économique 2023/2 (Vol. 74), pages 139 à 168 (SIGEM: analysis of the assignment procedure in major management schools)

"First, we list the expected properties of the assignments produced by the SIGEM. To do this we identify the SIGEM algorithm. It is quite standard in this type of environment since it is the “schools” version of the algorithm of Gale and Shapley [1962]. Based on this information, we show that assignments satisfy a stability property that is crucial in educational systems since it guarantees fair treatment of declared wishes and rankings. On the other hand, the use of this version of the algorithm of Gale and Shapley [1962], in opposition to the "candidate" version, raises two reservations concerning, on the one hand, the sub-optimality of the assignments from the point of view candidates and, on the other, the theoretical absence of simple strategies for candidates to play when submitting their wishes. This theoretical analysis of the algorithm is completed by a discussion on the specificities of the SIGEM procedure which can explain the formation of strategic behaviors. The second contribution concerns the use made of the results of this procedure in the case of SIGEM. We show how post-assignment data is used to determine the influential ranking of SIGEM from the so-called cross-dismissal matrix, itself based on the candidates' revealed preferences and their final assignments. The last contribution concerns the exploitation of a stylized fact which justifies the joint analysis of the algorithm and the SIGEM classification. The post-assignment data indeed reveal the existence of a hierarchy of schools that is very rigid and that achieves a consensus among students. This point is particularly interesting because it finally allows to have a finer look at the theoretical properties of the algorithm, the alignment of the preferences of the candidates tending to limit the impact of the negative effects associated with the use of the version "schools" of the algorithm of Gale and Shapley [1962]."

...

"Figure 2 presents for each school the number of ranked candidates and the number of wishes expressed for the school among these ranked. It seems to confirm the existence of these voluntary self-censorship strategies. In particular, we observe a significant loss for schools of average attractiveness (for example, AUDENCIA, NEOMA, SKEMA) which are more likely to be subject to both downward and upward truncation on the part of candidates ."



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Recall also, 

Strategic Issues in the French Academic Job Market, by Guillaume Haeringer, Vincent Iehlé In Revue économique Volume 61, Issue 4, 2010, pages 697 to 721

Friday, June 9, 2023

Decreasing kidney discards--review, and a call for clinical trials

 A review of discarded kidneys from a large OPO revealed only modest margins for improved utilization.

Bunnapradist, Suphamai MD1; Rosenthal, J. Thomas MD1; Huang, Edmund MD2; Dafoe, Donald MD3; Seto, Tom PharmD4; Cohen, Aaron BS4; Danovitch, Gabriel MD1. Deceased Donor Kidney Nonuse: A Systematic Approach to Improvement. Transplantation Direct 9(6):p e1491, June 2023. | DOI: 10.1097/TXD.0000000000001491

"Background. A large number of procured kidneys continue not to be transplanted, while the waiting list remains high.

"Methods. We analyzed donor characteristics for unutilized kidneys in our large organ procurement organization (OPO) service area in a single year to determine the reasonableness of their nonuse and to identify how we might increase the transplant rate of these kidneys. Five experienced local transplant physicians independently reviewed unutilized kidneys to identify which kidneys they would consider transplanting in the future. Biopsy results, donor age, kidney donor profile index, positive serologies, diabetes, and hypertension were risk factors for nonuse.

"Results.  Two-thirds of nonused kidneys had biopsies with high degree of glomerulosclerosis and interstitial fibrosis. Reviewers identified 33 kidneys as potentially transplantable (12%).

"Conclusions. Reducing the rate of unutilized kidneys in this OPO service area will be achieved by setting acceptable expanded donor characteristics, identifying suitable well-informed recipients, defining acceptable outcomes, and systematically evaluating the results of these transplants. Because the improvement opportunity will vary by region, to achieve a significant impact on improving the national nonuse rate, it would be useful for all OPOs, in collaboration with their transplant centers, to conduct a similar analysis."

...

"One posited cause for continued high nonuse rates is that transplant physicians are overly conservative, content with doing a small number of cases relative to the need. Both the existence of a “weekend effect”8 and a paper by French investigators stating 62% of kidneys not transplanted in the United States would be transplanted in France9 are used in support of this contention. Mistaken reliance on kidney biopsies is an additional factor implicated in inappropriate kidney nonuse.10 An alternative explanation is that transplant physicians and surgeons have not been persuaded that it is safe to transplant high-risk kidneys into older recipients based on retrospective registry studies.

"With this background in mind, and with a strong desire to respond to the imperative of increasing the use of heretofore nontransplanted kidneys, we undertook an analysis of unused kidneys in our OPO service area. Goal one was to understand the interplay of factors causing nonuse including donor demographics and biopsies. Goal two was to use the information from goal one to devise a plan to increase the kidney utilization rate in our service area.

"OneLegacy is the federally designated OPO for 7 counties in Southern California with a population of approximately 20 million. In 2019, which was chosen as the year of study because it was the last full year before the COVID-19 pandemic, OneLegacy served 10 centers with kidney transplant programs.11

"There were 1064 kidneys procured from 552 donors; 740 were transplanted and 324 were not transplanted. Forty-seven of the 324 (14.5%) were not offered for transplant because of absolute contraindications including cancers in the kidney, infections discovered during procurement, and abnormalities such as multicystic dysplastic kidneys. There were 5 surgical injuries (0.47%)—1 stripped ureter and 4 vascular injuries—all of which were determined to be nonrepairable by a transplant surgeon highly experienced with repair techniques. These kidneys were excluded from the study. The remaining 272 kidneys were offered for transplant and turned down by all local centers and, in turn, by all regional and national centers. Fourteen kidneys were provisionally accepted by and transported to nonlocal centers but, ultimately, not utilized due to prolonged cold ischemic times or findings on biopsies performed at the export center.

...

"One reason that the nonuse problem has proven intractable is that, even though it has been asserted that most nonused kidneys in the United States are safe to transplant, clinicians making the decisions in real time seem not to agree. Nor is there widespread enthusiasm for transplanting suboptimum kidneys into elderly recipients, despite papers promoting it,15 possibly because it is not entirely clear which older dialysis patients really benefit from transplantation.16

"The thought experiment of experienced local physicians reviewing procured but not transplanted kidneys appears to confirm this hypothesis. Despite French studies suggesting that 62% of kidneys not utilized in the United States would be transplanted in France, only 12% of kidneys were thus identified by our team of physicians, each of whom were highly motivated to reduce nonuse kidneys and highly knowledgeable about registry studies claiming safety of expanded donor criteria.10 If highly knowledgeable and experienced transplant physicians and surgeons—highly motivated to decrease nonuse—have not significantly changed kidney acceptance criteria, they are unlikely to be persuaded or respond to regulatory pressure to cause them to perform transplants that they feel would violate their responsibility to patients. Reducing the nonuse rate to ≤5% is unlikely under these conditions. Nonetheless, this experience does inform how improvement can occur.

"The alternative pathway to improvement in our service area is a more systematic prospective approach, in other words, an authentic clinical trial. The elements of such a trial would include codifying as precisely as possible the inclusion criteria for transplantable “suboptimal” donors, determining recipient criteria, extensive informed consent conversations, optimization of the organ offer process to minimize cold ischemia times, and outcomes tracking including quality of life and cognitive assessment. It should be decided in advance what will constitute an acceptable outcome for primary nonfunction and 1-y graft and patient survival."

Saturday, June 3, 2023

The critical role of Kelso & Crawford in the development of the stable matching literature

 In the physics literature there has long been an interest in economics (econophysics) that takes many forms. Here's a review of stable matching, which identifies Kelso and Crawford as a critical step in the evolution of the matching literature following Gale and Shapley.

Danilov, V.I. Review of the Theory of Stable Matchings and Contract Systems. Computational Mathematics and Mathematical Physics. 63, 466–490 (2023). https://doi.org/10.1134/S0965542523030065

"The real development was started by the work of Kelso and Crawford [123], who considered the more general problem of hiring workers (many-to-one). Their problem statement differed from the college admission problem in that the behavior of firms was more flexible than simply setting a quota in [81]. When hiring workers, the firm dealt with a “crowd” of candidates and chose the group of workers it needed from among this crowd. The description of the behavior of such a firm was no longer given by a simple ranking of candidates, but by a choice function. Below, we consider such functions in more detail. An important merit of Kelso and Crawford was that they found the “correct” condition on the choice function, which generalized the Gale–Shapley “linear” choice and which had previously appeared in economics as a substitutability condition. (Later it turned out that such a condition had already been introduced in the choice theory [152] under the name path independence.) Using this condition, Kelso and Crawford [123] showed that the Gale–Shapley algorithm works and gives a stable distribution of workers among firms. In [88], the notion of substitutability was used in the case of indivisible goods and led to a series of papers on this topic (see [79, 51, 65, 103]). Two years later, Roth [158] showed that the same substitutability condition also works well in a many-to-many situation, when firms could hire many workers and workers could work in several firms, see [62]. The results of this direction were summed up in the monograph [160]."