Characterizing group strategy-proof rules in the object allocation problem with money

We study the object allocation problem with money. The owner possesses a single object, and each agent has preferences that are not necessarily quasi-linear. We examine various group incentive properties, which are classified according to the following criteria: (i) whether the group incentive property is weak or strong, (ii) the maximum number of agents who may form a coalition, (iii) whether only self-enforcing manipulations are considered, (iv) whether agents in a coalition can reallocate the object among themselves after misrepresenting their preferences, and (v) whether agents in a coalition can arrange side payments among themselves. We characterize the classes of rules that satisfy various group incentive properties, along with a mild property of non-imposition. Furthermore, we establish the revelation principles for rules that satisfy the group incentive properties.