Efficiency, Sequenceability and Deal-Optimality in Fair Division of Indivisible Goods
This work addresses theoretical foundations for fair allocation mechanisms, relevant to computational social choice and resource distribution, but it is incremental as it builds on existing notions without introducing new paradigms.
The paper investigates connections between sequenceability and deal-optimality in fair division of indivisible goods with additive preferences, showing that an allocation is sequenceable if and only if it is optimal for certain cycle deals, and that Pareto-optimal allocations are sequenceable but not vice versa.
In fair division of indivisible goods, using sequences of sincere choices (or picking sequences) is a natural way to allocate the objects. The idea is as follows: at each stage, a designated agent picks one object among those that remain. Another intuitive way to obtain an allocation is to give objects to agents in the first place, and to let agents exchange them as long as such "deals" are beneficial. This paper investigates these notions, when agents have additive preferences over objects, and unveils surprising connections between them, and with other efficiency and fairness notions. In particular, we show that an allocation is sequenceable iff it is optimal for a certain type of deals, namely cycle deals involving a single object. Furthermore, any Pareto-optimal allocation is sequenceable, but not the converse. Regarding fairness, we show that an allocation can be envy-free and non-sequenceable, but that every competitive equilibrium with equal incomes is sequenceable. To complete the picture, we show how some domain restrictions may affect the relations between these notions. Finally, we experimentally explore the links between the scales of efficiency and fairness.