This is a technique that allows experts to forecast probabilities and possibilities anonymously in a number of structured rounds, each time refining ideas based on inputs from others. It was designed in the 1950s by Dalkey and Helmer of the Rand Corporation. Experts exchange views via an anonymous questionnaire or survey, independently reporting to a facilitator who collates and summarises those views. Subsequent questionnaires allow the experts to dig deeper, refine their ideas and reach consensus. The anonymity of the process allows them to save face, should they change their views.