Qualitative Forecasting Methods: Delphi Method

The Delphi Method
Originally developed by the RAND Corporation in 1969 for technological forecasting, the Delphi Method is a group decision process about the likelihood that certain events will occur. Today it is also used for environmental, marketing and sales forecasting.

The Delphi Method makes use of a panel of experts, selected based on the areas of expertise required. The notion is that well-informed individuals, calling on their insights and experience, are better equipped to predict the future than theoretical approaches or extrapolation of trends. Their responses to a series of questionnaires are anonymous, and they are provided with a summary of opinions before answering the next questionnaire. It is believed that the group will converge toward the "best" response through this consensus process. The midpoint of responses is statistically categorized by the median score. In each succeeding round of questionnaires, the range of responses by the panelists will presumably decrease and the median will move toward what is deemed to be the "correct" answer.

One distinct advantage of the Delphi Method is that the experts never need to be brought together physically, and indeed could reside anywhere in the world. The process also does not require complete agreement by all panelists, since the majority opinion is represented by the median. Since the responses are anonymous, the pitfalls of ego, domineering personalities and the "bandwagon or halo effect" in responses are all avoided. On the other hand, keeping panelists for the numerous rounds of questionnaires is at times difficult. Also, and perhaps more troubling, future developments are not always predicted correctly by iterative consensus nor by experts, but at times by "off the wall" thinking or by "non-experts".