Worldwide, metropolitan areas continue to be confronted by a growing number of increasingly difficult planning issues. It is our experience that planning practitioners have not taken full advantage of what the Delphi technique can contribute to making informed choices in a wide variety of decision and policy environments. The objectives of this paper are to describe and explain the research design that supported a real-world application of the Delphi technique in an urban, regional, and ecosystembased planning context, as well as to demonstrate how this model has been or can be adapted to serve a variety of planning research or application tasks.
Delphi is the site where the most revered oracles of ancient Greece formulated their predictions about the future (De Boer and Hale, 2000). In contrast to the predictions provided by the Pythia or priestesses, however, the research results derived from use of the Delphi technique are driven by methodological design. While instances of the use of the Delphi technique are evident in many disciplines, details regarding the employment of the technique in the planning literature have been scant since the 1980s. To address this void, we briefly outline the steps of the Delphi technique, and present methodological design findings from a real-world application of the technique used to derive the normative characteristics of high-quality plans generated within the framework of ecosystem-based planning. The paper concludes with lessons learned from that real-world exercise, which will be the subject of a companion paper.
The Delphi technique: background
The Delphi technique was developed by Dalkey and Helmer at the Rand Corporation in 1953 to explore the potential bombing strategies that Soviet military leaders might implement in the event of an atomic war (Dalkey, 1969; Helmer, 1983; Linstone and Turoff, 1975a; Rowe and Wright, 1999). The client of the Rand Corporation was the US Air Force, which recognized the complexity of the subject matter and needed a way to utilize the considerable expert knowledge on strategic bombing that existed in America after World War II.
Once the military applications of the Delphi technique were declassified in the 1950s and it was first publicly described in 1964, the technique entered the academic mainstream (Martino, 1999).
``Delphi may be characterized as a method for structuring a group communication process so that the process is effective in allowing a group of individuals, as a whole, to deal with a complex problem'' (Linstone and Turoff, 1975a, page 3).
In planning, the individuals involved in the group communication are typically planning experts. The structure of the group communication is designed by a monitor or monitor team that formulates a reiterative survey to address the research topic. The survey is sent to the designated group of experts (known as the Delphi panel) who then anonymously rank their preferences regarding a continuum of answers related to a series of questions or propositions posed. The experts subsequently return their responses to the Delphi monitor. Each of the iterative mail-outs (either by conventional mail or by e-mail) of the survey is called a round, and rounds continue until stable responses between rounds are achieved.
After the first round the monitor reviews and summarizes the responses, and then employs a measure of central tendency (usually the mean, median, or mode) to indicate where the majority of the panel responses are located on the response continuum. The response continuum can be based on Likert scale categories of five to seven points, or on some other rationale, in order to indicate the degree to which panel members agree or disagree with the questions or propositions posed (Critcher and Gladstone, 1998).
The monitor then develops a second-round survey that reveals the response dispersion of the panel, and also includes the feedback obtained from the first round's open-ended question(s) to ensure that the survey author has not overlooked something relevant to the topic. Upon receipt of the second round, the experts are asked to consider the position of the measure of central tendency of the panel, and are permitted to revise their initial responses if they choose. Although the process of response and reiteration can be repeated as many times as required, Delphi practice has revealed that the rate of response convergence is highest between rounds 1 and 2 (Linstone and Turoff, 1975a).
Although there are a number of different types of Delphi exercises, they can usually be assigned to one of three broad categories:
1. Normative Delphi. Normative Delphi exercises are explorations of what should be, given current knowledge (Martino, 1999). Obtaining consensus about a preferred future state or process is typically the primary research objective. An example of a normative Delphi includes the research of the authors, where a ten-member expert planning panel was employed to generate and measure agreement about the characteristics of highquality ecosystem-based plans (Novakowski, 1999). The Delphi technique was employed to derive an evaluation framework that was used to ascertain which plan form, plan content, and planning process conditions are necessary and sufficient for the evaluation of ecosystem-based plan quality. The results of the Delphi exercise were then subjected to metacriteria analysis and interpreted by employing hierarchy theory. The research results are presented in a forthcoming paper.