Ilan Fischer

Combining forecasts: What information do judges need to outperform the simple average?

Abstract Previous work has shown that combinations of separate forecasts produced by judgment are inferior to those produced by simple averaging. However, in that research judges were not informed of outcomes after producing each combined forecast. Our first experiment shows that when they are given this information, they learn to weight the separate forecasts appropriately. However, their judgments, though improved, are still not significantly better than the simple average because they contain a random error component. Bootstrapping can be used to remove this inconsistency and produce results that outperform the average. In our second and third experiments, we provided judges with information about errors made by the individual forecasters. Results show that providing information about their mean absolute percentage errors updated each period enables judges to combine their forecasts in a way that outperforms the simple average.

The Evolution of Cooperation in a Simulated Inter-Group Conflict

The present study simulates an enduring intergroup conflict in which each one of two interacting groups is represented by a unitary representative elected for a given constituency period. We assume that the conflict between the two groups can be modeled as an iterated Prisoner’s Dilemma game played by the groups’ representatives. In addition, we assume that the performance of each representative influences her constituents and that this, in turn, affects her prospects to be reelected. At the end of a constituency period, new elections are called for, and their results determine whether she remains in her position or is replaced by another representative. Our main objectives are: (1) to investigate the effect of this common democratic procedure, namely, the periodic election of group representatives, on the evolution of cooperation between the groups; and (2) to investigate the effect of the frequency of elections in the two groups on the evolving intergroup relations. Results of 150 simulations yield the following main results: (1) the dynamics of the intergroup conflict evolve into phases of welldefined patterns. (2) when mutual cooperation emerged, it was more enduring for high than for low rates of cooperation between the groups’ representatives; and (3) the prospects for reaching phases of mutual cooperation along the evolutionary path were considerably better for longer election periods, than for shorter ones.

Representation Methods and the Emergence of Inter-Group Cooperation

We report a simulation study which explores the effects of different representation methods and election frequencies on the emergence of mutual cooperation between two conflicting groups. We assume that the inter-group conflict can be modeled as an iterated Prisoner’s Dilemma game played by the groups’ representatives. In addition, we assume that the performance of each representative influences her constituents and that this, in turn, affects her prospects to be reelected. At the end of a constituency period, new elections are called for, and their results determine whether the delegate remains in her position or is replaced by another representative. Our main objectives were: (1) to investigate the effects of three representation methods: Random representation, Mean representation, and Minimal Winning Coalition representation, on the evolution of cooperation between the groups; and (2) to investigate the effect of the frequency of elections in the two groups on the evolving inter-group relations. Outcomes of 1080 simulations yield the following main results: (1) there exists an election frequency which optimizes the likelihood that the inter-group process converges to mutual cooperation; (2) similar cooperation characteristics evolve under the Minimal Wining Coalition and the Random representation methods; and (3) the Mean representation method results in low levels of inter-group cooperation.