Market Design


  • Organization of Live Donor Kidney Exchanges
  • Adoption of Children



  • Organization of Live Donor Kidney Exchanges (aka Kidney Paired Donation)

  • Kidney exchange: Here is a simple demo of the idea behind a two-way kidney exchange (from the Alliance for Paired Donation web-site). National Science Foundation web-published a story called "Kidney Exchange: A Life-Saving Application of Matching Theory about my research with Alvin E. Roth and Tayfun Sönmez on Kidney Exchange. The earlier achievements are surveyed in my survey paper with Tayfun Sonmez.
  • Establishment of the New England Kidney Exchange Program: Surgeon Frank Delmonico, Susan Saidman, Alvin E. Roth, Tayfun Sönmez, and I launched New England Program for Kidney Exchange (NEPKE) in 2004. This is the first program that uses optimization-based mechanisms to find kidney exchanges. NEPKE became the forerunner of the US National Kidney Exchange Program and dissolved itself in it in 2010. The administrator of NEPKE, Ruthanne Hanto, currently administors the national program.
  • Establishment of the Alliance for Paired Donation: Alvin E. Roth, Tayfun Sönmez, and I also helped the launching of the Alliance for Paired Donation (APD), founded by Dr. Michael Rees and Jon Kopke through the funding of University of Toledo and University of Cincinnati in Ohio. APD is a cross-country paired donation registry.
  • Establishment of the US National Kidney Exchange Program: The US National Kidney Exchange Program uses the similar principles with the APD exchange system. I served on the advisory board for the development of the program and coauthored the OPTN policy proposal for the principles of the national kidney paired donation program. Here is the US Congress Bill that clarified that paired kidney donations do not violate the National Organ Transplant Act and allowed for the establishement of the National Program.
  • Compatible pairs in kidney exchange: A compatible patient-donor pair typically does not participate in exchange, as the donor directly donates to the patient. However, in many occasions the donor of such a pair has a more valuable blood type (such as O) than that of the patient (such as A). Hence, if such pairs participated in exhange, they could potentially save an incompatible pair with reverse blood types (such as O patient - A donor) in addition to itself through a two-way exchange. Beginning with our original paper, "Kidney Exchange," we pushed this idea. A recent paper of mine, joint with Tayfun Sonmez, on campatible pairs in kidney exchange is "Altruistically Unbalanced Kidney Exchange."
  • Non-simultaneous non-directed altruistic donor chains: At APD, we started to implement Never-Ending-Altruistic-Donor Chains (NEAD-Chains), an idea that we developed with Michael Rees and Jon Kopke. Here is the Boston Globe and CNN news stories of the longest NEAD chain until March 2009, which has been documented in our recent NEJM paper. Also you can watch and read CBS evening news story featuring Matt Jones, the non-directed altruistic donor of the chain, surgeon Mike Rees, and some of the patients and donors of the chain. Recently a 30-way non-simulatenous non-directed altrustic donor chain has been reported. The National Kidney Registry (not to be confused with the US National Program) is currenty the leading organization that facilitates kidney exchanges and uses mostly NEAD chains.
  • Gains from larger exchanges: We showed in our AER paper "Efficient Kidney Exchange: Coincidence of Wants in Markets with Compatibility-Based Preferences" that using at-most 4-way exchanges, almost all gains from kidney exchange can be exploited. Based on this, we started to implement priority mechanisms using at most 4-way kidney exchanges in NEPKE and APD ( see a related news story). National program also uses 3-way exchanges.
  • Optimization and software: We have also authored the optimization software used in NEPKE and APD. However, solution of this optimization problem is in general NP complete. Thus, no efficient algorithm exists to find the outcome of our mechanisms. To handle a larger program, such as a national kidney exchange program, we proposed David Abraham, Avrim Blum and Tuomas Sandholm (computer scientists at CMU who are experts of designing memory efficient algorithms) to design an algorithm to find the outcomes of our mechanisms for larger problems. They have unveiled their algorithm that solves our proposals in 2007. National progarm uses this algorithm.
  • Earlier optimization and two-way exchanges: In our JET paper "Pairwise Kidney Exchange", besides our mechanism design approach, we propose using combinatorial optimization and graph theoretic techniques developed by Edmonds (1965) on organizing kidney exchanges. After we published `Pairwise Kidney Exchange' as an NBER working paper in the summer of 2004, Johns Hopkins team published a paper in 2005 in the Journal of American Medical Association with simulations using the generalized version of Edmonds' (1965) algorithm that we proposed in `Pairwise Kidney Exchange'. Consequently, in 2005, The Johns Hopkins University Transplant Center adopted a pairwise kidney exchange scheme based on Edmonds' algorithm.
  • Simultaneous non-directed altruistic donor chains: In our QJE paper "Kidney Exchange", we propose the idea of a "w-chain exchange." Non-directed altruistic donor chain exchanges are based on the same idea, and this second idea was developed by Johns Hopkins. Recently, Johns Hopkins University conducted the first 5-way non-directed donor chain exchange, in which a non-directed altruistic donor donates a kidney to the patient of the first pair, the donor of the first pair donates a kidney to the patient of the second pair, the donor of the second pair donates a kidney to the patient of the third pair, the donor of the third pair donates a kidney to the patient of the fourth pair, and finally the donor of the fourth pair donates a kidney to a waiting list patient without a donor.
  • Some other earlier notable press coverage:
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    Adoption of Children in State-wide Adoption Network of Pennsylvania

  • Mustafa Akan, Onur Kesten, and Vince Slaugh of Carnegie Mellon University and I have been working with State-wide Adoption Network (SWAN) of Pennsylvania to improve recommendation systems for suggesting families for adoptive children. Previous recommendation tools have been unsuccessful to be used by social workers distributed to different parts of the state, who are looking for best fits for the children up for adoption in the state network. They oftenby-passed recommendations made by the tools and used their own limited network for finding families. We have made some improvements to their system that aims to attain higher usage rates by social workers.