Delphi technique
Instead of attempting to ascertain the WTP for an environmental improvement or WTA for a degradation of it by individuals who may be irrational, impulsive or poorly informed, it is possible to employ a panel of experts and to elicit their views on the valuation of environmental changes. The technique was developed by the RAND Corporation in the 1950s (Dalkey and Helmer, 1963) and has been found to be particularly useful in cases where historical data are unavailable or where significant levels of subjective judgement are necessary (Smith, 1989). The method consists of the researcher assembling a panel of those who are believed to have some knowledge concerning the issue. It is important that the panel be from diverse fields, with different approaches and therefore different viewpoints and subjective valuations. The numbers in panels have ranged anywhere from four (Brockhoof, 1975) to over 900 (Shafer et al. 1974).
In the next stage the panel is given information on the study and asked for individual valuations. The responses are circulated to all panel members, who are asked if they wish to revise their own valuation in the light of the other responses. This process continues until some convergence of view between the experts, in the light of discussions with their colleagues, has occurred. And advantage of the method is that it requires little specialist statistical knowledge and is relatively simple to conduct, although the selection of an appropriate panel, and the design and wording of the questionnaire, are likely to have a crucial influence on the final outcome. Some may also view the process of valuation by so-called expert as undemocratic and artificial.
In discussing the environmental impact of tourism and means of assessing it, Hunter and Green (1995), in addition to canvassing expert opinions, emphasize the necessity for the local community to be involved in the decision-making process and valuable contribution it can make to directing or assisting the investigation of potentially significant impacts. Korca (1991) acknowledged the role of the expert and local residents in using the Delphi technique in a study of tourism development in the Mediterranean, in which a panel composed of representatives of both groups was assembled to identify the impact of continuing to expand tourism. Green and Hunter (1992) incorporated local public opinion when using the technique to assess redevelopment at a site in norther Britain. Green et al. (1990a1990b) also considered the more general application of the Delphi technique to tourism.