# What Is the Delphi Method, and How Is It Useful in Forecasting?

![Delphi Method](https://www.investopedia.com/thmb/Jcsk3xQQBYOj43v7Qd6GA0Dux9E=/1500x0/filters:no_upscale():max_bytes(150000):strip_icc()/Delphi-Method-Final-d9a01118a4d74e449269a1f25ad21382.jpg)

*A risk of the Delphi method is that experts may ultimately conform to groupthink. — Xiaojie Liu / Investopedia*

> **Definition**
>
> The Delphi method is a popular research tool that relies on authorities in a field reaching agreement on relevant issues.

## What Is the Delphi Method?

The Delphi method is a [forecasting](https://www.investopedia.com/terms/f/forecasting.asp) process and structured communication procedure that involves finding consensus of opinion via the anonymous responses of experts to questionnaires.

After each round of questionnaires, the experts are presented with an aggregated summary of the last round, allowing each expert to adjust their answers according to the group response.

This process combines the benefits of expert analysis with elements of the wisdom of crowds.

### Key Takeaways

*   The Delphi method depends on group opinion or decision for its conclusions.
*   Experts respond to several rounds of questionnaires; anonymous responses are aggregated and shared with the group after each round.
*   The experts can adjust their answers based on how they interpret the group response provided to them.
*   The ultimate result is meant to be a true consensus of what the group thinks.

## Understanding the Delphi Method

Several rounds of questionnaires are sent out to the group of experts, and the anonymous responses are aggregated and shared with the group after each round.

The experts are allowed to adjust their answers in subsequent rounds, based on how they interpret the group response that has been provided to them.

Since multiple rounds of questions are asked and the panel is told what the group thinks as a whole, the Delphi method seeks to reach the correct response through consensus.

The Delphi method was originally conceived in the 1950s by Olaf Helmer and Norman Dalkey of RAND Corp. The name refers to the Oracle of Delphi, a priestess at the temple of Apollo in ancient Greece known for her prophecies.

The Delphi method allows experts to work toward a [mutual agreement](https://www.investopedia.com/terms/m/meeting-of-the-minds.asp) by conducting a circulating series of questionnaires and releasing related feedback to further the discussion with each subsequent round.

The experts’ responses shift as rounds are completed based on the information brought forth by other experts participating in the analysis.

> **Important**
>
> The Delphi method was developed in the early 1950s "to obtain a reliable expert consensus, which is often used as a substitute for empirical evidence when it does not exist."

## Delphi Method Process

First, the group facilitator selects a group of experts based on the topic being examined. Once all participants are confirmed, each member of the group is sent a questionnaire with instructions to comment on each topic based on their personal opinion, experience, or previous research.

The questionnaires are returned to the facilitator, who groups the comments and prepares copies of the information. A copy of the compiled comments is sent to each participant, along with the opportunity to comment further.

At the end of each comment session, all questionnaires are returned to the facilitator, who decides if another round is necessary or if the results are ready for publishing.

The questionnaire rounds can be repeated as many times as necessary to achieve a general sense of consensus.

## Advantages of the Delphi Method

The Delphi method seeks to aggregate opinions from a diverse set of experts, and it can be done without having to bring everyone together for a physical meeting.

Since the responses of the participants are anonymous, individual panelists don’t have to worry about repercussions related to their opinions.

The anonymity of the participants also helps prevent the “halo effect,” which sees higher priority given to the views of more powerful or higher-ranking members of the group.

By conducting Delphi studies, consensus can be reached over time as opinions are swayed, making the method very effective.

In contrast with many other types of interviews and focus groups, Delphi studies allow participants to rethink and refine their opinions based on the input of others, contributing to a more reflective and thoughtful process.

## Disadvantages of the Delphi Method

Although it provides the benefits of anonymity and the possibility for reevaluation and reflection, the Delphi method does not result in the same sort of interactions as a live discussion.

A live discussion can sometimes produce a better example of consensus, as ideas and perceptions are introduced, broken down, and reassessed.

Response times using the Delphi method can be long, which slows the rate of discussion. It is also possible that the information received back from the experts will provide no innate value.

The deliberate and drawn-out nature of the Delphi method also presents some challenges. Since the method often requires multiple rounds of questionnaires, there is a chance that some participants may drop out from the study before it has been completed.

In addition, while there are benefits to giving participants the opportunity to reassess their views, there is a chance that they will adjust their responses so that they are more closely aligned with the views of the majority, reducing the diversity of opinions represented and diminishing the validity of the results.

## Applications of the Delphi Method

Let's take a look at some general examples of when and how the Delphi method can be applied. This list is not meant to be exhaustive, but consider these options:

*   [**Healthcare and Medicine**](https://www.investopedia.com/terms/h/health_care_sector.asp): The Delphi method is frequently used in healthcare to forecast future medical advancements. Experts collaborate to predict technological innovations such as new diagnostic tools and treatment methods, ensuring that healthcare providers are prepared for future challenges. We'll take a look at more specific examples in the next section.
*   **Education**: In the field of education, the Delphi method helps in curriculum development, future needs assessment, and policy formulation. Educators and industry experts work together to identify the skills and knowledge necessary for future graduates, shaping curricula that a broader group has agreed upon (or at least collaborated on).
*   **Business and Management**: Businesses utilize the Delphi method for strategic planning, market forecasting, and identifying critical success factors. By engaging with industry experts, companies can anticipate market trends, threats, and areas of growth. There are more niche examples here, too. For instance, marketing professionals use the method to predict consumer behavior and product demand.
*   **Environmental Studies**: Environmental researchers use the Delphi method to assess risks, predict climate change impacts, and develop sustainability strategies. Experts forecast potential environmental hazards and their consequences as part of the Delphi method here.
*   [**Public Policy**](https://www.investopedia.com/government-and-policy-4689793): The Delphi method also plays a part in setting public policy. Policymakers collaborate with experts to create comprehensive policy frameworks that tackle complex issues like healthcare reform or economic inequality.
*   **Transportation**: Transportation planning leans in on the Delphi method by forecasting traffic patterns, planning infrastructure projects, and developing policies. Experts predict future traffic trends that legislative officials can then use to shape reform.
*   **Military and Defense**: Much like in business, the Delphi method supports military and defense planning by aiding in strategic planning, threat assessment, and resource allocation. However, military strategists also use it to anticipate future threats, conflicts, and security challenges to national security; this could expand to cyberattacks, terrorism, or much smaller-scale risks.
*   [**Tourism and Hospitality**](https://www.investopedia.com/financial-edge/0212/5-ways-to-invest-in-travel-and-tourism.aspx): The tourism and hospitality industry also can use the Delphi method to forecast trends. As with other industries, experts predict travel trends and tourist preferences, helping destinations and businesses plan for future demand. This industry is very diverse, and the Delphi method helps aggregate some of the differing perspectives.

## Example of the Delphi Method

The objective of one medical study was to develop guidelines for monitoring high-risk medications. The study aimed to assess the prevalence of laboratory testing.

As part of the study guidelines, an advisory committee of national experts and local leaders employed a two-round internet-based Delphi process to identify key medications that require monitoring.

The Delphi method achieved consensus on the medications to be included in the guidelines within those two rounds. The guidelines covered 35 drugs or drug classes and 61 lab tests. The findings brought some attention to the fact that despite general agreement on the importance of laboratory monitoring for high-risk medications, actual monitoring practices are inconsistent.

Therefore, the study found that even though there was a positive general consensus towards lab monitoring, there was some variability in this.

## Alternatives to the Delphi Method

If the Delphi method doesn't quite sound like the methodology for you, there are many other similar yet technically different methods. Below are some alternative examples.

*   **Nominal Group Technique (NGT)**: Under NGT, experts independently generate ideas on a topic and then share these ideas in a round-robin format. Unlike the Delphi method, NGT involves face-to-face interactions and immediate ranking and discussion.
*   **Brainstorming:** Brainstorming (or [ideation](https://www.investopedia.com/terms/i/ideation.asp)) occurs when a group of experts gathers to freely generate ideas and solutions. The goal is to produce as many ideas as possible which are later reviewed and refined. Brainstorming focuses on generating a large quantity of ideas through spontaneous and uninhibited thinking, whereas the Delphi method is more structured and iterative.
*   **Focus Groups**: Focus groups are small, diverse groups of experts that engage in guided discussions to explore a specific topic in-depth. Focus groups involve real-time, interactive discussions with immediate feedback, while the Delphi method uses iterative rounds of anonymous questionnaires.
*   **Surveys/Questionnaires**: When using surveys, experts provide their opinions and insights through structured questionnaires. Surveys gather data in a single round or a few rounds without the iterative feedback loop characteristic of the Delphi method.
*   **Interviews**: One-on-one interviews with experts provide insights (and maybe some opinions) on a specific topic. While interviews involve direct, personal interaction and in-depth exploration of individual viewpoints, the Delphi method is more anonymous and usually with bigger groups.
*   **Workshops**: Finally, let's touch on workshops. Workshops are interactive sessions where experts collaborate to address specific problems. Like some of the other bullets above, workshops involve real-time collaboration and hands-on activities, whereas the Delphi method uses a structured, iterative process.

## What Is the Delphi Method Used for?

The Delphi method is used to establish a consensus opinion about an issue or set of issues by seeking mutual agreement from a group of experts in the relevant field. The Delphi method has been used to conduct research in numerous areas, from the defense industry to healthcare.

## How Is the Delphi Method Conducted?

The group facilitator selects a group of experts based on the topic being examined and sends them a questionnaire with instructions to comment on each topic based on their personal opinion, experience, or previous research. The facilitator groups the comments from the returned questionnaires and sends copies to each participant, along with the opportunity to comment further. At the end of this session, the questionnaires are returned to the facilitator, who decides if another round is necessary or if the results are ready for publishing. This process can be repeated multiple times until a general sense of consensus is reached.

## How Is Consensus Defined When Using the Delphi Method?

Although the Delphi method seeks to pinpoint an area of mutual agreement among the pool of experts, it is unlikely that the participants will be in complete agreement on all issues, even after several rounds of questionnaires and opportunities for reassessment. Researchers applying the Delphi method may have different thresholds for exactly what constitutes a consensus, and some critics of the method point to the subjective nature of this determination as a shortcoming.

## How Many Rounds Are Generally Conducted in a Delphi Study?

Generally, a Delphi study is conducted in two to four rounds. The exact number of rounds will vary depending on the study's objectives and the complexity of the issue being addressed with a higher number of rounds needed for more advanced topics.

## The Bottom Line

The Delphi method uses multiple rounds of questionnaires sent to a panel of experts to work toward a mutual agreement or consensus opinion. The participants modify their responses based on the information brought forth by other experts participating in the analysis.

The Delphi method benefits from the anonymity of the participants and the opportunities it provides for reassessment. But it also can be time-consuming and, in some cases, may be less effective than a live discussion or focus group.  

> **Article Sources**
>
> 1.  The RAND Corp. “[An Experimental Application of the Delphi Method to the Use of Experts](https://www.rand.org/content/dam/rand/pubs/research_memoranda/2009/RM727.1.pdf).”
>     
> 2.  RAND. "[Generating Evidence Using the Delphi Method](https://www.rand.org/pubs/commentary/2023/10/generating-evidence-using-the-delphi-method.html#:~:text=The%20Delphi%20method%20was%20developed,when%20it%20does%20not%20exist.)."
>     
> 3.  Barrett, David, and Roberta Heale. “[What Are Delphi Studies?](https://ebn.bmj.com/content/ebnurs/23/3/68.full.pdf)” _Evidence-Based Nursing_, vol. 23, no. 3, July 2020, pp. 68-69.
>     
> 4.  National Library of Medicine. "[Development and Pilot Testing of Guidelines to Monitor High-Risk Medications in the Ambulatory Setting](https://pubmed.ncbi.nlm.nih.gov/20645664/)."