Many patients in need of a kidney transplant have a willing but incompatible (or poorly matched) living donor. Kidney exchange programs arrange exchanges among such patient-donor pairs, in cycles and chains of exchange, so each patient receives a compatible kidney. Kidney exchange has become a...

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...

An organ transplant can improve a patient's life while also realizing substantial savings in healthcare expenditures. Like many other scarce public resources, organs from deceased donors are rationed to patients on a waitlist via a sequential offer mechanism. The theoretical trade-offs in...

It has been previously shown that for sufficiently large pools of patient-donor pairs, (almost) efficient kidney exchange can be achieved by using at most 3-way cycles, i.e. by using cycles among no more than 3 patient-donor pairs. However, as kidney exchange has grown in practice, cycles among...

As multi-hospital kidney exchange clearinghouses have grown, the set of players has grown from patients and surgeons to include hospitals. Hospitals have the option of enrolling only their hard-to-match patient-donor pairs, while conducting easily arranged exchanges internally. This behavior has...

We show that kidney exchange markets suffer from traditional market failures that can be fixed to increase transplants by 25%-55%. First, we document that the market is fragmented and inefficient: most transplants are arranged by hospitals instead of national platforms. Second, we propose a...

This note describes the unraveling of transaction dates in several markets, including the labor markets for new lawyers hired by large law firms and for gastroenterology fellows, and the market for post-season college football bowls. Together these will illustrate that unraveling can occur in...

This essay discusses some things we have learned about markets, in the process of designing marketplaces to fix market failures. To work well, marketplaces have to provide thickness, i.e. they need to attract a large enough proportion of the potential participants in the market; they have to...

The deferred acceptance algorithm proposed by Gale and Shapley (1962) has had a profound influence on market design, both directly, by being adapted into practical matching mechanisms, and, indirectly, by raising new theoretical questions. Deferred acceptance algorithms are at the basis of a...

This essay examines how repugnance sometimes constrains what transactions and markets we see. When my colleagues and I have helped design markets and allocation procedures, we have often found that distaste for certain kinds of transactions is a real constraint, every bit as real as the...