Ulric B. and Evelyn L. Bray Social Sciences Seminar
Unpaired Kidney Exchange: Overcoming Double Coincidence of Wants without Money (with Julien Combe, Yinghua He, Victor Hiller, Robert Shimerk and Olivier Tercieux)
Abstract: For an incompatible patient-donor pair, kidney exchanges often forbid receipt-before-donation (the patient receives a kidney before the donor donates) and donation-before-receipt, causing a double-coincidence-of-wants problem. Our proposal, the Unpaired kidney exchange algorithm, uses "memory" as a medium of exchange to eliminate these timing constraints. In a dynamic matching model, we prove that Unpaired delivers a waiting time of patients close to optimal and substantially shorter than currently utilized state-of-the-art algorithms. Using a rich administrative dataset from France, we show that Unpaired achieves a match rate of 57 percent and an average waiting time of 440 days. The (infeasible) optimal algorithm is only slightly better (58percent and 425 days); state-of-the-art algorithms deliver less than 34 percent and more than695 days. We draw similar conclusions from the simulations of two large U.S. platforms. Lastly, we propose a range of solutions that can address the potential practical concerns of Unpaired.
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