3.9 Adjustment for Uncertainty
A primary concern with the results of many CV studies is that individuals have little or no
Experience in providing valuation responses to what may be unfamiliar environmental
Goods. A closely related concern is the single-shot nature of most valuation exercises in
Hypothetical markets, and that individual preferences may be highly uncertain. One
pathway to addressing these concerns is allowing respondents to express the degree of
uncertainty of their valuation responses, and incorporating this information in WTP
models (Berrens et al. 2002).
Respondents in CV surveys sometimes over-express their valuation of the good in a
hypothetical scenario, resulting in what is often termed “hypothetical bias.” In order to
mitigate hypothetical bias, certainty responses must be adjusted. A number of approaches
have emerged for incorporating respondent’s uncertainty. These typically involve a postdecision
question that asks the individual how certain he/she is of his/her response to the
CV question. The format of this follow-up can be on a qualitative scale
(e.g., “fairly sure”or “absolutely sure”) or a numeric certainty scale such as a 10-point Likert scale in which 1=very uncertain and 10=very certain (Murphy et al. 2004).