Firms and workers may sign complex contracts that govern many aspects of their interactions. I show that when firms regard contracts as substitutes, bargaining over contracts can be understood as bargaining only over wages. Substitutes is the assumption commonly used to guarantee the existence...

We define the empirical content of an economic theory as the least restrictive observationally equivalent theory. We show that the empirical content of a theory is captured by a certain kind of axiomatization, with axioms that are universal negations of conjunctions of atomic formulae.

Organs for transplantation are a scarce resource. Paying to increase the supply of organs is illegal in much of the world. We review efforts to increase transplantation by increasing the supply of available organs from living and deceased donors. Progress has been made in increasing the...

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...

Organ donations from deceased donors provide the majority of transplanted organs in the United States, and one deceased donor can save numerous lives by providing multiple organs. Nevertheless, most Americans are not registered organ donors despite the relative ease of becoming one. We study in...

The design of the New York City (NYC) high school match involved trade-offs among efficiency, stability, and strategy-proofness that raise new theoretical questions. We analyze a model with indifferences -- ties -- in school preferences. Simulations with field data and the theory favor breaking...