Using contingent valuation to elicit public preferences for water fluoridation

The methods and results of a contingent valuation survey to elicit public preferences for water fluoridation are reported. The study demonstrates that not only is it important to acknowledge that there will be losers from the introduction of such a programme but that losers must be allowed to express a value for the magnitude of their perceived loss. Two methods of valuing this loss are explored. Conventional willingness to accept compensation questions are compared with questions in which losers are asked to state their willingness to pay to prevent their water being fluoridated. The results provide tentative support for asking willingness to pay to prevent questions instead of willingness to accept questions when evaluating certain types of public good. The issue of protest responses in contingent valuation surveys is also highlighted and discussed.     

Treating respondent uncertainty in contingent valuation: A comparison of empirical treatments

This research examines the impact of uncertainty on contingent valuation responses using (1) a survey of Canadian landowners about willingness to accept compensation for converting cropland to forestry and (2) a survey of Swedish residents about willingness to pay for forest conservation. Five approaches from the literature for incorporating respondent uncertainty are used and compared to the traditional random utility model with assumed certainty. The results indicate that incorporating uncertainty has the potential to increase fit, but could introduce additional variance. While some methods for uncertainty can be an improvement over traditional approaches, it is imperative to exercise caution when making systematic judgments about the effect of uncertainty on contingent valuation responses.     

Comparing continuous and discrete contingent valuation questions

This paper explores two commonly used methods to elicit an individual's willingness to pay (WTP) for a public good in contingent valuation studies. Currently, the most preferred method is the take-it-or-leave valuation question, or discrete valuation question (DVQ), where the respondent accepts or rejects a suggested cost for the good. The traditional method, the continuous valuation question (CVQ), simply asks an individual to state his WTP for the suggested change in the provision of a public good like cleaner air. We introduce a simple way to compare the results from these two methods. We also test the anchoring behavior suggested in the psychological literature on choice under uncertainty. The results do not support the anchoring hypothesis, but suggest the hypothesis that people perceive the two tested valuation questions differently.I would like to thank Prof. Glenn Harrison, University of South Carolina, Prof. P-O Johansson, Stockholm School of Economics, Prof. Jason Shogren, Iowa State University, and two referees for helpful comments. The usual disclaimer applies.     

Effect of substitutes in contingent valuation for a private market good

Economic theory predicts a decrease in valuation as the availability of substitutes increases. This paper describes a contingent valuation (CV) survey that investigates the effect of substitutes on valuation of private market goods. Using an approach that compares willingness to pay (WTP) values elicited from a CV question that accounts for substitutes with WTP values elicited from a similar question without substitutes, we find that allowing for substitutes can moderate WTP values. For the item valued in this study, a hamburger sandwich, allowing for substitutes was associated with a reduction of from 10% to 16% in stated values.     

Contingent valuation and actual payment for voluntarily provided passive-use values: Assessing the effect of an induced truth-telling mechanism and elicitation formats

A fundamental question about the contingent valuation (CV) method is to what degree it predicts actual payments (AP). This has particularly been an intriguing matter related to voluntary provision of public goods representing primarily passive-use values. This paper reports the results from such a CV–AP comparison. Applying a voluntary payment mechanism there exists a theoretical expectation of upward bias in CV estimates and downward bias in AP. This study applied an induced truth-telling mechanism in one treatment group to assess the hypothetical bias effect in CV. The CV estimates in this treatment group were significantly lower than in the group that did not face this mechanism. But this effect was limited to those responding/acting to dichotomous choice, not affecting those responding to open-ended questions about willingness to pay.     

Starting point bias and respondent uncertainty in dichotomous choice contingent valuation surveys

In this article, we develop a dichotomous choice model with follow-up questions that describes the willingness to pay being uncertain in an interval. The initial response is subject to starting point bias. Our model provides an alternative interpretation of the starting point bias in the dichotomous choice valuation surveys. Using the Exxon Valdez survey, we show that, when uncertain, individuals tend to answer “yes”.     

Preference uncertainty in contingent valuation

In this paper, the results of empirical studies that applied two widely used methods - numerical certainty scale (NCS) and polychotmous choice (PC) - for estimating preference uncertainty adjusted willingness to pay (WTP) in contingent valuation (CV), are summarized. For this review, a number of conclusions are reached. First, there is a lack of consensus about which method is more appropriate for measuring preference uncertainty. Second, although preference uncertainty information has been found useful in detecting the incidence of hypothetical bias in CV studies, a consensus about a standard certainty threshold (or treatment mechanism) at which hypothetical behaviour converges to real behaviour is yet to emerge. Third, insufficient empirical evidence exists about the causal relationship between preference uncertainty scores and the theoretically expected explanatory variables. Finally, the preference uncertainty adjusted PC and NCS models fail to provide a consistent and more efficient welfare estimate compared to the conventional dichotomous choice certainty model.     

Willingness and ability of Bulgarian consumers to pay for improved public health care services

An application of the contingent valuation method to the willingness and ability of Bulgarian consumers to pay for public health care services is presented. The study uses data from a household survey conducted in May–June 2000. The willingness and ability to pay for outpatient, inpatient and dental services is investigated. A combination of interval checklist and open-ended questions are used to elicit the willingness-to-pay amounts. The impact of the sociodemographic characteristics on the responses is examined by a generalized Tobit regression. Based on the regression equation, the welfare effects of various fee levels are simulated.     

A Semi-parametric Estimator of Willingness-to-pay Applied to Dichotomous Choice Contingent Valuation Data

The use of dichotomous choice questions (Are you willing to pay $x?) has been advocated as superior to open ended questions (What would you be willing to pay?) in contingent valuation studies of non‐market goods. A supplementary dichotomous choice question, raising or lowering the bid price depending on the initial response, gives increased precision. However, a problem with these methods is that identifying the mean willingness to pay (WTP) is more complex, and often conditional on making a distributional assumption. This paper will present a semi‐parametric method for estimating WTP without invoking any such assumptions, using the interval inherent in the double bounded format, and based on estimating the underlying hazard function for the distribution of WTP. An advantage of the approach over other non‐parametric methods is that it allows one to include respondent characteristics as determinants of the individual decisions, and does so within a computationally straightforward framework.     

Stated Preferences, Real Behaviour and Anchoring: Some Empirical Evidence

We compare different contingent valuation question formats with each other and with observed behaviour for a non-monetary estimation task, the expected number of kilometers travelled by automobile. Open-ended questions, open-ended follow-up questions, dichotomous choice (DC) questions, and double-bound DC questions are included. The single and double-bound DC questions result in an estimated mean about twice as high as the actual value and the open-ended mean. The DC question overestimation seems to be due to an anchoring effect leading to yea-saying behaviour. Our results about the difference between DC questions and open-ended questions is consistent with the pattern observed in contingent valuations studies of the willingness to pay. Our results indicates that DC questions seem to be associated with a general overestimation problem that is present even for simple non-monetary estimation tasks.     

A multilevel modelling approach to triple-bounded dichotomous choice contingent valuation

The use of dichotomous choice (DC) questions in the elicitation of willingness to pay (WTP) in contingent valuation studies is common practice at the present time. Recent research has shown that double-bounded DC questions provide statistically superior results to single-bounded questions, given an appropriate sampling design. This paper uses a relatively new multilevel modelling technique to analyze a triple-bounded DC design, which in addition includes an initial non-monetary question on whether an individual accepts, in principle, a WTP some unspecified amount. The theoretical basis of the multilevel model used is described, and some of the possibilities of this potentially powerful and versatile technique are discussed. The practical operation of the multilevel model is demonstrated using data from a contingent valuation study conducted in the Norfolk Broads, England, an internationally important wetland resource.     

A comparison of empirical models used to infer the willingness to pay in contingent valuation

The essence of the contingent valuation method consists of creating a hypothetical market where respondents are asked about their willingness to pay (WTP) for a non-market good. Different empirical models can be formulated to estimate the expected WTP of a sample of respondents and, then, through aggregation, the social valuation of the good is inferred.This paper outlines the relevance of the distributional assumptions when estimating mean WTP. Several parametric and non-parametric methods are discussed and applied to calculate the existence value of a natural space. Results show that WTP is extremely sensitive to the empirical model used.First version received: November 2002 / Final version received: January 2004     

Comparing Fuzzy and Probabilistic Approaches to Preference Uncertainty in Non-Market Valuation

In seeking to value environmental amenities and public goods, individuals often have trouble trading off the (vague) good or amenity against a monetary measure. Valuation in these circumstances can best be described as fuzzy in terms of the amenity being valued, perceptions of property rights, and the numbers chosen to reflect values. In this paper, we apply fuzzy logic to contingent valuation, employing a fuzzy clustering approach for incorporating preference uncertainty obtained from a follow-up certainty confidence question. We develop a fuzzy random utility maximization (FRUM) framework where the perceived utility of each individual is fuzzy in the sense that an individual’s utility belongs to each cluster to some degree. The model is then applied to a Swedish survey that elicited residents’ willingness to pay for enhanced forest conservation and to a Canadian survey of agricultural landowners that elicited their willingness to accept compensation for a tree planting program. Both the WTP and WTA measures we obtain using the fuzzy approach are well below those obtained using standard probability methods. Based on goodness of fit measures and Monte Carlo experimentation, a case can be made for using a fuzzy preference approach for modeling preference uncertainty as opposed to incorporating respondent uncertainty within the random utility maximization framework.      

A comparison of contingent valuation method and random utility model estimates of the value of avoiding reductions in king mackerel bag limits

This paper estimates the value of king mackerel bag limit changes with both stated and revealed preference methods. The 1997 Marine Recreational Fishery Statistical Survey allows estimation of the value of avoiding bag limit reductions with the random utility model and the contingent valuation method. Using the contingent valuation method, the willingness to pay to avoid a one fish reduction in the bag limit is $2.45 per year. Using the random utility model, the willingness to pay to avoid a one fish reduction in the bag limit is $2.24 per trip and $7.71 for a two-month time period. Considering several methodological issues, the difference in willingness to pay between the stated and revealed preference methods is in the expected direction.     

Does Question Format Matter? Valuing an Endangered Species

A three-way treatment design is used to compare contingent valuation response formats. Respondents are asked to value an endangered species (the red-cockaded woodpecker) and the restoration of its habitat following a natural disaster. For three question formats (open-ended, payment card, and double-bounded dichotomous choice), differences in survey response rates, item non-response rates, and protest bids are examined. Bootstrap techniques are used to compare means across formats and to explore differences in willingness to pay (WTP) distribution functions. Convergent validity is found in a comparison of mean WTP values, although some differences are apparent in the cumulative distribution functions. Differences across formats are also identified in item non-response rates and proportion of protest bids. Overall, the payment card format exhibits desirable properties relative to the other two formats.     

Willingness to pay for a Green Energy program: A comparison of ex-ante and ex-post hypothetical bias mitigation approaches

The most persistently troubling empirical result in the contingent valuation method literature is the tendency for hypothetical willingness to pay to overestimate real willingness to pay. Two approaches, ex-ante and ex-post, have been developed to mitigate or eliminate the overstatement of hypothetical willingness to pay. The ex-ante approach addresses hypothetical bias in the survey design stage while the ex-post approach addresses hypothetical bias with follow-up questions to the hypothetical willingness to pay question. We find that willingness to pay estimates are similar when either the ex-ante or ex-post approach are employed. Our results suggest that the approaches should be considered as complements and not substitutes. Employing both approaches to mitigate hypothetical bias we estimate that the annual benefits of the regional amenities associated with a Green Energy program in North Carolina are $186 million.     

Can Hypothetical Questions Reveal True Values? A Laboratory Comparison of Dichotomous Choice and Open-Ended Contingent Values with Auction Values

Can hypothetical questions reveal true values? An examination of thelaboratory experimental literature examining contingent valuation (CV)lends some support for using open-ended hypothetical willingness to payquestions. However, experimental studies examining dichotomous choicehave found that hypothetical answers overstate demand. Consistent withthe experimental literature, published CV studies comparing open-ended todichotomous choice questions have shown that values from the dichotomouschoice method equal or exceed those of the open-ended method in everycase. This paper presents a series of experiments employing more than 800subjects to test this hypothesis for CV and compares the CV results toactual auction values in a single controlled experimental environment.     

Actual averting expenditure versus stated willingness to pay

The purpose of this study is to perform a complete comparison of actual averting expenditure and stated willingness to pay measures, and to determine if the averting expenditure is a lower bound of the willingness to pay measured from contingent valuation experiment as suggested by literature. In addition to the single value comparison, Bootstrap, Krinsky and Robb, Jackknife, and Cameron are four simulation methods used to calculate confidence intervals for response function. Sample sizes of 100, 200, and 1000 are simulated 100 and 200 times respectively. A set of data with 540 households from a contingent policy referendum survey is employed for our purpose. Under a specific level of BOD improvement, a one-to-one single mean value comparison of the actual averting expenditure is greater than the mean willingness to pay from utility difference model. The empirical results are consistent with the theoretical expectation for expenditure difference that averting expenditure is a lower bound of willingness to pay generated from the contingent valuation method. A confidence interval, which contains the true mean willingness to pay at least 90% of the times, includes the actual averting expenditure as a lower bound of the mean willingness to pay as theory predicts.     

Cost credibility and the stated preference analysis of public goods

Two recent stated preference studies include questions that explore participants’ beliefs regarding the cost amount stated in the valuation question in relation to the cost to them if the project were implemented. Results from these studies suggest that a significant proportion of people do not believe these stated cost amounts. This paper explores the implications of participants answering valuation questions that are not consistent with their beliefs regarding stated costs. As an example, the paper develops a response model for dichotomous choice stated preference questions. Participants gather project information through the stated preference experiment, form a prior distribution of costs, update the distribution of costs based on a survey's stated cost and then respond to the dichotomous choice stated preference question. The model suggests that participants will not generally respond truthfully in the sense that they may say no to a stated cost that is less than their willingness to pay for a project or yes to a stated cost that is more than their willingness to pay. While the model findings suggest potentially serious problems with stated preference estimation, the observed patterns of disbelief from the empirical studies result in downwardly biased estimates of mean willingness to pay.     

Commodity prices as payment vehicles in valuation experiments

Many contingent valuation experiments use commodity prices as the payment vehicle. In this note it is shown, in general, that this approach does not allow the investigator to extract the respondent's willingness to pay. However, it is also shown how the valuation question can be formulated so as to yield a commodity price payment vehicle which is equivalent to a lump sum payment.The idea for this paper came while teaching the Royal Economic Society Easter School in Birmingham (March/April 1995). I am grateful to my students for stimulating discussions and comments on the subject. Kerry Smith provided me with (as always) insightful comments on an