In priority-based matching problems, there is a trade-off between efficiency andreducing justified-envy. We show that finding an efficient and justified-envy minimalmatching is an NP-hard problem when objects have weak priority rankings. Consequently, we focus on resolving the trade-off in a...

Allocation and exchange of discrete resources such as kidneys, school seats, and many other resources for which agents have single-unit demand is conducted via direct mechanisms without monetary transfers. Incentive compatibility and efficiency are primary concerns in designing such mechanisms....