[UTMD-067] Reallocation-proofness in object reallocation problems with single-dipped preferences (by Yuji Fujinaka, Takuma Wakayama)

We examine the problem of reallocating indivisible objects among agents with single-dipped preferences with respect to a fixed order of objects. Our main axiom, reallocation-proofness, requires that no pair of agents can benefit by misrepresenting their preferences and swapping their assignments. In this setting, by invoking the recent work of Hu and Zhang (2024), we find that the top trading cycles rule (TTC) is characterized by individual rationality, strategy-proofness, and reallocation-proofness. Building on this, we extend the analysis in two directions. First, we explore the case where only pairwise exchanges are permitted, and show that under this constraint, the characterization of TTC holds even without strategy-proofness. Second, we consider a more general model where objects are arranged in a tree structure instead of in a line, and demonstrate that the characterization of TTC can be extended to this general setting as well.