Bargaining and the theory of cooperative games: John Nash and beyond

This essay surveys the literature on the axiomatic model of bargaining formulated by Nash ("The Bargaining Problem," Econometrica 28, 1950, 155-162).Nash's bargaining model, Nash solution, Kalai-Smorodinsky solution, Egalitarian solution

Weighted Proportional Losses Solution

We propose and characterize a new solution for problems with asymmetric bargaining power among the agents that we named weighted proportional losses solution. It is specially interesting when agents are bargaining under restricted probabilistic uncertainty. The weighted proportional losses assigns to each agent losses proportional to her ideal utility and also proportional to her bargaining power. This solution is always individually rational, even for 3 or more agents and it can be seen as the normalized weighted equal losses solution. When bargaining power among the agents is equal, the weighted proportional losses solution becomes the Kalai-Smorodinsky solution. We characterize our solution in the basis of restricted monotonicity and restricted concavity. A consequence of this result is an alternative characterization of Kalai-Smorodinsky solution which includes contexts with some kind of uncertainty. Finally we show that weighted proportional losses solution satisfyies desirable properties as are strong Pareto optimality for 2 agents and continuity also fulfilled by Kalai-Smorodinsky solution, that are not satisfied either by weighted or asymmetric Kalai-Smorodinsky solutions.

Gradual Negotiations and Proportional Solutions

I characterize the proportional N-person bargaining solutions by individual rationality, translation invariance, feasible set continuity, and a new axiom - interim improvement. The latter says that if the disagreement point d is known, but the feasible set is not - it may be either S or T, where S is a subset of T - then there exists a point d' in S, d' > d, such that replacing d with d' as the disagreement point would not change the final bargaining outcome, no matter which feasible set will be realized, S or T. In words, if there is uncertainty regarding a possible expansion of the feasible set, the players can wait until it is resolved; in the meantime, they can find a Pareto improving interim outcome to commit to - a commitment that has no effect in case negotiations succeed, but promises higher disagreement payoffs to all in case negotiations fail prior to the resolution of uncertainty.Bargaining; Proportional solutions

Bargaining with random arbitration: an experimental study

We use a laboratory experiment to study bargaining in the presence of random arbitration. Two players make simultaneous demands; if compatible, each receives the amount demanded as in the standard Nash demand game. If bargainers’ demands are incompatible, then rather than bargainers receiving their disagreement payoffs with certainty, they receive them only with exogenous probability 1−q. With probability q, there is random arbitration instead, with one bargainer randomly selected to receive his/her demand and the other bargainer receiving the remainder. The bargaining set is asymmetric, with one bargainer favoured over the other. We set disagreement payoffs to zero, and vary q over several values ranging from zero to one. Our main experimental results support the directional predictions of standard game theory (though the success of its point predictions is mixed). In the spirit of typical results for conventional arbitration, we observe a strong chilling effect on bargaining for values of q near one, with extreme demands and low agreement rates in these treatments. For the most part, increases in q reinforce the built-in asymmetry of the game, further benefiting the favoured player at the expense of the unfavoured player. The effects we find are non-uniform in q: over some fairly large ranges, increases in q have minimal effect on bargaining outcomes, but for other values of q, a small additional increase in q leads to sharp changes in results.Nash demand game, random arbitration, chilling effect, equilibrium selection,experiment.

Weighted proportional losses solution

We propose and characterize a new solution for problems with asymmetric bargaining power among the agents that we named weighted proportional losses solution. It is specially interesting when agents are bargaining under restricted probabilistic uncertainty. The weighted proportional losses assigns to each agent losses proportional to her ideal utility and also proportional to her bargaining power. This solution is always individually rational, even for 3 or more agents and it can be seen as the normalized weighted equal losses solution. When bargaining power among the agents is equal, the weighted proportional losses solution becomes the Kalai-Smorodinsky solution. We characterize our solution in the basis of restricted monotonicity and restricted concavity. A consequence of this result is an alternative characterization of Kalai-Smorodinsky solution which includes contexts with some kind of uncertainty. Finally we show that weighted proportional losses solution satisfyies desirable properties as are strong Pareto optimality for 2 agents and continuity also fulfilled by Kalai-Smorodinsky solution, that are not satisfied either by weighted or asymmetric Kalai-Smorodinsky solutions

Bargaining Multiple Issues with Leximin Preferences

Global bargaining problems over a finite number of different issues, are formalized as cartesian products of classical bargaining problems. For maximin and leximin bargainers we characterize global bargaining solutions that are efficient and satisfy the requirement that bargaining separately or globally leads to equivalent outcomes. Global solutions in this class are constructed from the family of monotone path solutions for classical bargaining problems.Global bargaining, maximin preferences, leximin preferences