A Justified Envy Minimal Variation of the Top Trading Cycles Mechanism

For priority-based allocation of indivisible objects to agents with unit demand, when each object has exactly one copy, Abdulkadiroglu et al. (2019) show that the priority-based top trading cycles mechanism is justified envy minimal, in the sense that no strategy proof and Pareto efficient mechanism has strictly less justified envy than it. It remains open whether there is a unique justified envy minimal mechanism. We propose a strategy proof and Pareto efficient variation of the top trading cycles mechanism and show that it is also justified envy minimal.