In this paper, we axiomatically study how to measure the similarity of preferences in a group of individuals. For simplicity, we refer to this as the cohesiveness. First, we provide axioms that characterize a family of linear and additive measures whose intersection is a partial ordinal criterion similar to first order stochastic dominance. The introduction of some additional properties isolates a one-parameter subfamily. This parameter evaluates the effect on the cohesiveness if one individual changes his ranking on a single pair of objects, as a function of how many of the remaining individuals in the group rank the first object over the second and vice versa. Finally, we characterize the focal measures of this subfamily separately showing that they coincide with measures constructed using two, at first sight, totally different approaches suggested in the literature.

The cleaning up of waste present in transboundary rivers, which requires the cooperation of different authorities, is a problematic issue, especially when responsibility for the discharge of the waste is not well-defined.Following Ni and Wang [12] we assume that a river is a segment divided into several regions from upstream to downstream. We show that when the transfer rate of the waste is unknown, the clean-up cost vector provides useful information for estimating some limits in regard to the responsibility of each region. We propose a cost allocation rule, the Upstream Responsibility rule, which takes into account these limits in distributing costs "fairly" and we provide an axiomatic characterization of this rule via certain properties based on basic ideas concerning the responsibility of regions.JEL classification: C71; D61

There is a wide range of economic problems that involve the exchange of indivisible goods with no monetary transfers, starting with the housing market model of the seminal paper by Shapley and Scarf (1974) and including other problems such as kidney exchange or school choice problems. The classical solution to many of these models is to apply an algorithm/mechanism called Top Trading Cycles, attributed to David Gale, which satisfies good properties for the case of strict preferences. In this paper, we propose a family of mechanisms, called Top Trading Absorbing Sets mechanisms, which generalizes the Top Trading Cycles to the general case in which individuals are allowed to report indifferences, while preserving all its desirable properties.

The closeness (or cohesiveness) of preferences in a preference profile has mainly been measured by aggregating the distances between each pair of preferences. We argue in this paper that some important information is lost in this process and we opt for considering the profile as a whole when constructing such a measure. With this idea in mind, we propose axioms a cohesiveness measure should satisfy and show that these properties fully characterize a new family of measures.

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