In this reply I describe the unraveling of transaction dates in several markets, including the labor market for new lawyers hired by large law firms. This and other markets illustrate that unraveling can occur in markets with competitive prices, that it can result in substantial inefficiencies, and that marketplace institutions play a role in restoring efficiency. All of these contradict the conclusions of Priest.

The growth of kidney exchange presents new challenges for the design of kidney exchange clearinghouses. The players now include directors of transplant centers, who see sets of patient-donor pairs, and can choose to reveal only difficult-to-match pairs to the clearinghouse, while withholding easy-to-match pairs to transplant locally. This reduces the number of transplants. We discuss how the incentives for hospitals to enroll all pairs in kidney exchange can be achieved, and how the concentration of hard to match pairs increases the importance of long, non-simultaneous nondirected donor chains.