Jury Size and the Free Rider Problem

In recent times, judges in the United States have said that 6‐person juries are inferior to 12‐person juries. But by what reasoning is a smaller jury inferior? One argument is the Condorcet jury theorem, which says that a larger jury will reach a more accurate decision. This, however, assumes that the information of each juror is independent of the size of the jury. I show that a juror's information does depend on the size of the jury. In a larger jury panel each juror has less incentive to pay attention in the court, even though they are all pledged to hear and deliver a verdict on a trial. Because of the free‐rider problem, a larger jury may actually make poorer decisions. The results apply to many environments in which decisions are made by committees and work teams.