A case study of long-term Delphi accuracy

We evaluated the long-term accuracy of predictions from a Delphic poll of the future of the mental health profession [1]. Six hundred participants provided predictions about the likely occurrence and probable time courses for 18 scenarios that could possibly have occurred over the 30-year interval between 1981 to present. Each of the panelists was polled twice with distributional feedback from the first poll provided on the second poll questionnaires. The data from the second polling was used to make predictions regarding the future of various issues that may have affected the mental health profession over the forecast interval. It has now been 30 years since the original poll was conducted; the purpose of this study was to evaluate the accuracy of the original group predictions. Results indicated that the Delphi panelists correctly predicted the occurrence of 14/18 scenarios. For those scenarios that did occur, the time course predictions were accurate within approximately 1–5 years.

► We evaluated accuracy of the Delphi Method over a 30 year time frame.
► Predictions of if an event would occur were correct for 14 of 18 scenarios.
► Predictions of when the occurring events would occur were accurate within 1–5 years.