Thirteen theorems in search of the truth

We review recent work on the accuracy of group judgmental processes as a function of (a) the competences (judgmental accuracies) of individual group members, (b) the group decision procedure, and (c) group size. This work on individual competence and group accuracy represents an important contribution to democratic theory and a useful complement to the usual emphasis in the social choice literature on individual preference and preference aggregation mechanisms. The work reported on is rooted in a tradition which goes back to scholars such as Condorcet, Poisson, and Bayes.