An outline of the Delphi technique of long-range forecasting by separately eliciting and refining the opinions of a group of advisers without contact among them, and calculating a statistical "group response." The procedure was designed to overcome the disadvantages common to committees and small groups. The experts reply to written questionnaires or an online computer, receive statistical feedback through formal lines of communication, and resubmit their estimates. Where the response is a number (such as a date or amount), the most useful index has been the median of the individual estimates. During the process, opinions do converge; where answers can be checked against reality, it is found that the median response tends to move in the direction of the true answer. Self-confidence is not correlated with individual performance, but the subgroup with the highest self-ratings for competence will consistently perform slightly better than the group as a whole.