 The majority rule is of course only one way to aggregate judgments. The Delphi method (e.g., Dalkey and Helmer 1963; for an application to medicine, see Jones and Hunter 1995) applies to cases where the task is to provide a numerical estimate of some variable of interest (say, the risk difference a new treatment makes). Experts answer questionnaires in several rounds. After each round, a facilitator provides an anonymous summary of the experts’ estimates from the previous round and the reasons given for their judgments. Experts are thus supposed to be encouraged to revise their earlier answers in light of other experts’ estimates and justifications. During this process the range of the estimate will often decrease, and it is hoped that the group will converge towards the correct answer. The process is stopped after a pre-determined stopping criterion such as number of rounds, achievement of consensus, stability of results, and an average of the estimates of the final round is used as result.