Delphi Survey


A Delphi Survey is a series of questionnaires that allow experts to develop ideas about potential future developments around an issue. The questionnaires are developed throughout the process in relation to the responses given by participants.


Delphi Surveys are used to gather collective forecasts through questionnaires about likely or possible developments in particular areas. Delphi Surveys can be carried out face to face, online or by post. In online versions, participants are given their own login and password to access the site. This is useful when the expert participants are very busy people.

The technique aims to derive the benefit of the opinions of a group of experts, while avoiding the disadvantages of 'group-think' and group dynamics where certain individuals dominate the discussion. It is believed that during this process the range of the answers will decrease and the group will converge towards the "correct" answer.

The process takes place in a number of stages:

  • The first questionnaire either asks the participants to individually identify issues and generate as many ideas as possible or to answer more close ended questions such as the likely dates for specific developments.
  • The second questionnaire anonymously feeds back all the ideas and forecasts sent in the first round to all participants. This questionnaire also provides space for participants to refine each idea, comment on their strengths or weaknesses and to suggest new ideas.
  • An additional questionnaire then summarises the input from the second questionnaire and asks for further clarification, strengths, weaknesses, and new ideas. This stage can be repeated as many times as necessary until consensus on key points is reached.
  • The end product is either a consensus amongst the participants on likely and possible future developments, or a wide range of possible developments and their relative strengths and weaknesses.

Used for

The first applications of the Delphi method were in the field of science and technology forecasting, and this remains its main use. Topics the method has been used for tend to focus on scientific breakthroughs and have included population controlautomation, space progress, war prevention and weapon systems, vehicle-highway systems, industrial robots, intelligent internet, broadband connections, and technology in education. It has also been applied to public policy issues like economic trends, health and education  and business forecasting.


  • People are chosen to participate in a Delphi Survey because of their expertise or specific knowledge of the topic area. This expertise does not have to be academic and could instead be the knowledge of an experienced service user.
  • It is important that the participants reflect a wide range of views and perspectives so that there will be a meaningful exchange of ideas.
  • A Delphi survey may involve 10 to 50 participants.



  • As the Delphi survey is often run as a remote method, it does not have costs for venues or transport. However, the cost of sending surveys by post or setting up the survey online remains.
  • It can sometimes be suitable to provide an incentive for the participants, such as a small payment.

Approximate time expense


  • As the participants in a Delphi Survey are often very busy, it is sometimes necessary to allow them plenty of time (weeks, if not a month) to complete each round of surveys.
  • It is quite time consuming to remind and encourage participants to complete the surveys.
  • It is important that participants are aware of the level of time commitment required in advance of joining as the many rounds can be demanding.


  • Participants can complete the surveys in their own time.
  • Can include a wide range of expertise.
  • People can freely express their opinions and critique ideas as anonymity is maintained throughout the process.
  • Discussions are not dominated by one participant's authority or personality.
  • The series of questionnaires generates a much wider set of ideas than each individual participants would generate by completing them independently.
  • Results will not be skewed towards influential individuals.
  • A rapid consensus can be achieved.
  • Participants do not have to be in the same room together to reach agreement.
  • Relatively low cost to administer and analyse
  • There is the potential to gain large quantities of data


  • Success of the method depends on the quality of the participants.
  • It may be hard to coordinate and motivate the group.
  • The written response format may be less suitable for some potential respondents.
  • Results may be influenced by the collective bias of the participants or the facilitators analysis.
  • The surveys are limited to forecasting future developments and are unable to recommend action.
  • Will not build relationships or generate a dialogue between participants.
  • Does not cope well with widely differing opinions or large changes in opinions (paradigm shifts).
  • Can be time-consuming.


The Delphi Method was developed by the Rand Corporation for the American military as way of forecasting future technological developments. Since then, it has been widely used in the field of science and technology forecasting to combine expert opinion on the likelihood and impact of technological developments, particularly on warfare.


Image by Lukas CC0 License