Sharing Variable Returns of Cooperation

Abstract

A finite set of agents jointly undertake a project. Depending on the aggregate of individual agent characteristics the project runs losses or profits, which have to be shared. This paper adopts the mechanistic view and concentrates on devices that a contingent planner may use in order to share the net profits. The Moulin and Shenker (1994) representation theorem is used to show that additive mechanisms with the constant returns property relate 1 to 1 to rationing methods. Refinements are discussed dealing with monotonicity and equity properties that relate to the dispersion of shares. The second part introduces the notion of a consistent solution. Each rationing method induced by a consistent mechanism is consistent. If such mechanism is continuous as well, then the corresponding rationing method is parametric in the terminology of Young (1998) and Moulin (2000). Most prevalent mechanisms (average, serial, Shapley-Shubik) are consistent as member of the class of incremental mechanisms. Each interval consistent incremental mechanism is shown to be a composition of marginal mechanisms and the average mechanism. Immediately the average mechanism is the unique strongly consistent solution. Finally a characterization of mechanisms within the general class is discussed using super-additivity.