Aggregation of individual judicial or juror decisions

Up to this point we have analysed courts or legal decision making 'as if' the individuals engaged in that process have clear, rational objectives - regarding efficiency, fairness, or some other criteria. But legal decisions - and in fact many, if not most forms of economic policy - are often undertaken as collective decision-making processes. Legal rules and precedents are often formed as a result of a mechanism that attempts to develop a consensus between judges, jurors, or tribunal members. More formally, courts or judicial bodies (such as juries) often take decisions based on an aggregation rule. An aggregation rule simply takes the individual decisions or preferences of individuals over a set of outcomes and produces an aggregate or group ranking of those outcomes. An alternative way to think about an aggregation rule is that it takes information from individual decision makers regarding the desirability of alternatives, processes it, and produces a summary of this information, which is then used to provide a picture of the 'overall' desirability of each of the alternatives.

This section explores some of the issues involved in aggregation. There are several major complications which arise in the analysis of such aggregation rules or procedures:

  • 1. There may be very few (if any) aggregation rules whose outcomes obey a 'reasonable' or desirable set of properties or axioms;
  • 2. The outcome of some aggregation rules may be very sensitive to the choice of rule, even though underlying preferences do not change and even though the rule is changed in relatively minor ways;
  • 3. Some rules may be highly susceptible to strategic preference manipulation by certain individuals.

A complete analysis of all of these issues is beyond the scope of this book. We instead conclude this chapter by studying one of the most important arguments as to why group decisions may be superior to individual decisions.

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