A Learning Design for Reducing Hypothetical Bias in the Contingent Valuation Method

Over the last few years a great deal of research has focussed on hypothetical bias in value estimates obtained with the contingent valuation (CV) method and on means for ameliorating if not eliminating such bias. To date, efforts to eliminate hypothetical bias have relied on calibration techniques or on word-smithing of one kind or another to induce subjects to provide responses to hypothetical questions that mimic responses made by subjects facing actual payments in the valuation experiment. This paper introduces a different approach for eliminating hypothetical bias. A design for a CV survey format is presented which provides subjects with the opportunity to learn how the CV institution works. Sequential referenda are conducted where respondents gain experience in CV settings by participating in both hypothetical and real referenda. The logic of this Learning Design is a straightforward application of the trials process used in experimental economics. We demonstrate that the Learning Design is effective in eliminating hypothetical bias in surveys concerning donations to two different public goods.     

Provision Point Mechanisms and Field Validity Tests of Contingent Valuation

Past field validity tests of contingent valuation have relied on voluntary contribution mechanisms to elicit actual willingness to pay, and may overestimate hypothetical bias because of free riding in the actual contributions. This paper argues that provision point mechanisms are a preferred alternative for field validity tests of contingent valuation because they increase the proportion of demand revealed in cases in which public goods can be provided in a step function. The results of a contingent valuation validity study of participation in a green electricity pricing program that uses a provision point mechanism are reported, and hypothetical open-ended and dichotomous choice responses are compared to actual participation. Calibration of hypothetical responses is also explored.     

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.     

Giving Stated Preference Respondents “Time to Think”: Results From Four Countries

Previous studies have found that contingent valuation (CV) respondents who are given overnight to reflect on a CV scenario have 30–40% lower average willingness-to-pay (WTP) than respondents who are interviewed in a single session. This “time to think” (TTT) effect could explain much of the gap between real and hypothetical WTP observed in experimental studies. Yet giving time to think is still rare in binary or multinomial discrete choice studies. We review the literature on increasing survey respondents’ opportunities to reflect on their answers and synthesize results from parallel TTT studies on private vaccine demand in four countries. Across all four countries, we find robust and consistent evidence from both raw data and multivariate models for a TTT effect: giving respondents overnight to think reduced the probability that a respondent said he or she would buy the hypothetical vaccines. Average WTP fell approximately 40%. Respondents with time to think were also more certain of their answers, and a majority said they used the opportunity to consult with their spouse or family. We conclude with a discussion of why researchers might be hesitant to adopt the TTT methodology.     

Donation Payment Mechanisms and Contingent Valuation: An Empirical Study of Hypothetical Bias

Donation payment mechanisms are well suited forsome contingent valuation studies. In aneffort to better understand the discrepancythat has been consistently found between actualand hypothetical donations, we investigate anapproach to estimating actual willingness todonate using contingent donations with afollow-up question in which respondents ratethe level of certainty about their response tothe contingent donation question. The approachallows us to estimate the magnitude of thehypothetical bias and identify the respondentsresponsible for the bias. Identification ofthe respondents responsible for thehypothetical bias is the first step towarddeveloping an understanding of the causes andpossible remedies. In this study we find thatmost of the respondents (80%) to thecontingent donation question provide a responseconsistent with how we predict they wouldrespond in an actual donation situation.     

Improving the Performance of Contingent Valuation Studies in Developing Countries

This paper discusses three main reasons why so many of the contingentvaluation studies conducted in developing countries are so bad. First,the contingent valuation surveys themselves are often poorly administeredand executed. Second, contingent valuation scenarios are often very poorlycrafted. Third, few CV studies conducted in developing countries aredesigned to test whether some of the key assumptions that the researchermade were the right ones, and whether the results are robust with respectto simple variations in research design and survey method. The paper concludesthat research on stated preference methods in developing countries iscritically important to the successful implementation of these methodsbecause (1) there is no empirical evidence to suggest that rapid,”streamlined” CV surveys yield reliable, accurate results, and (2)there is a significant risk that the current push for cheaper, simplerCV studies could discredit the methodology itself. Moreover, the policydebates to which CV researchers are asked to contribute are often oftremendous importance to the well-being of households in developingcountries. Because the costs of policy mistakes can prove tragic, itis critical that VC researchers push for excellence in this researchenterprise and that funding agencies think more carefully about thevalue of policy-relevant information in the fields in which thecontingent valuation method is being used to study household preferencesand behavior (e.g., water and sanitation services, urban air pollution,soil erosion, deforestation, biodiversity, watershed management,ecosystem valuation, vaccines for the poor).     

Why do people non-demand reveal in hypothetical double referenda for public goods?

Hypothetical contingent valuation surveys used to elicit values for environmental and other public goods often employ variants of the referendum mechanism due to the cognitive simplicity and familiarity of respondents with this voting format. One variant, the double referendum mechanism, requires respondents to state twice how they would vote for a given policy proposal given their cost of the good. Data from these surveys often exhibit anomalies inconsistent with standard economic models of consumer preferences. There are a number of published explanations for these anomalies, mostly focusing on problems with the second vote. This article investigates which aspects of the hypothetical task affect the degree of nondemand revelation and takes an individual-based approach to identifying people most likely to non-demand reveal. A clear profile emerges from our model of a person who faces a negative surplus i.e. a net loss in the second vote and invokes non self-interested, non financial motivations during the decision process.     

Testing competing models of loss aversion: an adversarial collaboration

This paper reports an ‘adversarial collaboration’—a project carried out by two individuals or research groups who, having proposed conflicting hypotheses, seek to resolve their dispute. It describes an experiment which investigates whether, when individuals consider giving up money in exchange for goods, they construe money outlays as losses or as foregone gains. This issue bears on the explanation of the widely observed disparity between willingness-to-pay (WTP) and willingness-to-accept (WTA) valuations of costs and benefits, which has proved problematic for contingent valuation studies. The results of the experiment are broadly consistent with the hypothesis that money outlays are perceived as losses.     

Use of Contingent Valuation to Elicit Willingness-to-Pay for the Benefits of Developmental Health Risk Reductions

We report the results of several contingent valuation (CV) surveys to elicit willingness-to-pay values from the general public for risk reductions associated with decreases in exposure to a chemical, PCBs, in the environment. We also develop Quality Adjusted Life Years (QALYs) from the survey using both standard gamble and time-tradeoff elicitation methods to explore the relationship between QALYs and willingness-to-pay (WTP), and to develop QALY weights for subtle developmental effects. The results of the CV surveys are designed for incorporation into a case study of an integrated risk model to monetize the benefits of predicted risk reductions. Respondents showed a nearly proportional, positive relationship between decreasing the risk of a 6-point reduction in IQ (a standard measure of “intelligence”) and WTP, but showed a negative relationship between risk reduction and WTP for reading comprehension as an outcome. The range of mortality risks that respondents would accept on behalf of their (hypothetical) 10-year-old child is 2 in 10,000 to 9 in 1,000 per IQ point, and WTP per IQ point is $466 ($380, $520). QALY weights elicited via time tradeoff (reduction in life expectancy) were significantly different from QALY weights elicited via a standard gamble (p = 0.001). Respondents who answered questions about ecological endpoints first were willing to pay a small additional amount when asked about human health effects, but those respondents who answered questions about human health endpoints first were not willing to pay any additional amount when subsequently asked about ecological effects. This paper has not been submitted elsewhere in identical or similar form, nor will it be during the first three months after its submission to the Publisher.     

Willingness to Pay and Sensitivity to Time Framing: A Theoretical Analysis and an Application on Car Safety

Stated preference (SP) surveys attempt to obtain monetary values for non-market goods that reflect individuals’ “true” preferences. Numerous empirical studies suggest that monetary values from SP studies are sensitive to survey design and so may not reflect respondents’ true preferences. This study examines the effect of time framing on respondents’ willingness to pay (WTP) for car safety. We explore how WTP per unit risk reduction depends on the time period over which respondents pay and face reduced risk in a theoretical model and by using data from a Swedish contingent valuation survey. Our theoretical model predicts the effect to be nontrivial in many scenarios used in empirical applications. In our empirical analysis we examine the sensitivity of WTP to an annual and a monthly scenario. Our theoretical model predicts the effect from the time framing to be negligible, but the empirical estimates from the annual scenario are about 70 % higher than estimates from the monthly scenario.     

Fairness in the contingent valuation of environmental public goods: attitude toward paying for environmental improvements at two levels of scope

Respondents to contingent valuation (CV) surveys give a variety of reasons for not wanting to pay money. This variability is likely to reflect people's attitudes toward paying for the public good change, their attitudes toward paying for public goods in general, and a component that is independent of these attitudes but unique to particular beliefs about paying (e.g. ‘I can't afford to pay’). Negative attitudes toward paying can contribute to an apparent insensitivity to different levels of the same public good. In a telephone survey, northern Wisconsin property owners were asked about their WTP for four environmental public goods (biodiversity, Indian spearfishing, water quality, and wolves) at two levels of scope (part and whole). For water quality and spearfishing, the part was a chain of lakes that was geographically nested within a larger region of lakes. Similarly, the biodiversity whole represented a region comprising the smaller level of the public good. The scope conditions for wolves were quantitatively nested levels of returning 300 and 800 wolves to northern Wisconsin. Respondents’ beliefs about paying for each public good and level of scope were measured in order to test their generality across the different public goods and levels of scope. Negative attitudes toward paying that are general across public goods place restrictions on the use of CV for environmental public goods. However, negative attitudes that are tied to specific environmental public goods suggest that the valuation method might be difficult to implement in these cases only. Moreover, negative attitudes toward paying that are either general or specific may contribute to perfect embedding when they are expressed across different levels of scope for the same public good. Respondents' beliefs about paying for each public good were associated with an attitude toward paying for the respective good and an attitude toward paying for public goods in general at both levels of scope. The general attitude was more explanatory of beliefs about paying for wolf reintroduction and spearfishing than were the specific attitudes. The distribution of beliefs was sensitive to the type of good being valued, but less so to the scope of the public good change. Contingent valuation practitioners should seek improvements in respondents' perceptions of the fairness of the valuation process in order to facilitate citizens' involvement in decisions about environmental public goods. Avenues for future research are proposed and discussed.     

Valuing Global Ecosystem Services: What Do European Experts Say? Applying the Delphi Method to Contingent Valuation of the Amazon Rainforest

Valuing global public goods like the Amazon rainforest by stated preference surveys of a representative sample of the global population would be very costly and time consuming. We explore the use of the Delphi Method in contingent valuation (CV) by asking a panel of 49 European environmental valuation experts in two rounds what they think would be the result if a European CV survey of Amazon Rainforest protection plans was conducted. The experts’ best guess for the mean willingness-to-pay (WTP) by European households for preserving the current Amazon Rainforest, and thus avoiding a predicted loss in forest area by 2050 from currently 85% to 60% of the original forest in the 1970s, was 28 € per household annually as an additional income tax. Aggregated over all European households this amounts to about 8.4 billion € annually. This preliminary estimate indicate that WTP of distant beneficiaries is substantial, and could justify preservation of global ecosystem services where aggregated benefits of the local population often do not exceed the opportunity costs of preservation in terms of lost income from commercial activities. The income elasticity of WTP with respect to per-capita income in the European countries is 0.5–0.6. Recognizing the limitations and assumptions of the Delphi CV method, it could still be a time saving and cost-effective benefit transfer tool for providing international donors with much needed order-of-magnitude estimates of the non-use value of ecosystem services of global significance.     

Exchange Rules and the Incentive Compatibility of Choice Experiments

The incentive properties of stated-preference surveys continue to be a central debate in the valuation of public goods. The majority of empirical studies have focused on incentive properties of contingent valuation questions in relation to situations where answers have monetary consequences. This research explores the incentive properties of repeated, attribute-based choice questions when subjects are provided with an explicit connection between choices and outcomes. Two market/provision-rules are investigated: a posted-price market and a plurality-rule vote. These two provision rules are contrasted to treatments in which no provision rule is discussed—subjects are simply asked to choose their preferred alternative. These three hypothetical choice treatments are compared with a binding choice treatment. While none of the public good treatments are theoretically incentive compatible, we include a comparison of hypothetical and binding choices for a private-good that is incentive compatible. The private good experiments indicate that marginal willingness to pay (WTP) estimates from the hypothetical treatment are larger, but not statistically different than corresponding estimates in the binding choice treatment. Results for the public good experiments indicate that marginal WTP estimates from the hypothetical treatments are much larger, and statistically different than corresponding estimates in the binding choice treatment. The bias is largest when no provision rule is discussed. The bias is reduced with the inclusion of a provision rule, but surprisingly, there was no difference across provision rule treatments. Overall, our results indicate that choice experiments involving a public good should include a provision rule to reduce bias, but the resulting marginal WTP estimates may still be more biased, on average, than those arising from contingent valuation survey formats.     

Researching Preferences,Valuation and Hypothetical Bias

A number of recent papers in environmental economics have focused on the process of researching preferences – agents are uncertain about preferences but with effort may narrow their uncertainty. This issue has arisen in formulating bids in contingent valuation (CV) as well as the debate over the divergence between WTP and WTA. In the context of CV, it has been suggested that the hypothetical nature of the preference elicitation process biases responses. This paper provides both a theoretical model and experimental evidence to contribute to this debate. The model is a model of competitive bidding for a private good with two components that are particularly relevant to the debate. The first component is that bidders are unsure of their own value for the private good but may purchase information about their own value (researching preferences). The second component is that there is a probability that the auction is hypothetical – that the winning bidder will not get the private good and will not pay the winning bid. The experiment tests this theoretical model of bidding equilibrium and analyzes the effects of variations in the parameters (hypotheticalness, information costs and number of agents) on the endogenous variables (such as the proportion of bidders who become informed and the winning bid). Experimental results suggest that an increase in the hypotheticalness of an auction tends to decrease the likelihood that bidders pay for information on their valuation with an ambiguous effect on the winning bid.      

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     

Induced-Value Tests of Contingent Valuation Elicitation Mechanisms

Using an induced-value experimental design that varies whether values for a “good” are certain or uncertain and whether payment is real or hypothetical, this study investigates issues of demand revelation, hypothetical bias, and value uncertainty for four elicitation mechanisms used in contingent valuation surveys: dichotomous choice, dichotomous choice with follow-up certainty question, payment card, and multiple-bounded discrete choice. For all elicitation mechanisms, we find no evidence of hypothetical bias: voting decisions do not vary systematically when payment is hypothetical versus when it is real. Under all design conditions we find the fewest deviations between stated and induced values and the strongest evidence of demand revelation with dichotomous choice. Stated uncertainty in dichotomous choice follow-up and multiple-bounded discrete choice questions does correlate with uncertain induced values, but the signal is noisy. We discuss the implications of our findings for the design of contingent valuation surveys.     

WILLINGNESS TO PAY FOR DESERT PROTECTION

This paper uses a referendum-style survey approach known as dichotomous-choice contingent valuation to estimate the benefits of restricting the uses of 6.9 million acres of desert land. Statistical techniques estimate the value to California residents of creating three new national parks and 76 new wilderness areas in the high and low deserts of eastern California. The total amount that California residents would be willing to pay to enact desert protection legislation ranges from $177 million to $448 million per year. This estimate hinges on the assumptions that (i) the residents who did not complete and return the survey questionnaire ("nonrespondents") would receive no benefits from desert protection and (ii) the estimate of willingness to pay for the "respondents" is unbiased.     

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.     

The impact of the bird flu on public willingness to pay for the protection of migratory birds

In this paper, we present the results of a unique time series analysis of contingent values and models for migratory bird protection based on an identical contingent valuation (CV) survey carried out over a three year time period since the first bird flu outbreak in 2003. Although there exists no scientific evidence for a direct relationship, migratory birds are believed to play an important role in spreading the bird flu virus worldwide. The time series analysis allows us to test the temporal stability of stated preferences for migratory bird protection and at the same time examine indirectly the possible impact of increased media attention and public awareness levels regarding the bird flu. We test the impact of the bird flu on public willingness to pay (WTP) for migratory bird protection in the final 2005 survey whilst accounting for procedural variance introduced by sequencing and question ordering-effects, but we are unable to demonstrate a direct negative relationship. A novelty of the study presented here is that respondents in the CV surveys are given the opportunity to pay an annual money amount or a one-time-off lump-sum. Annual WTP values appear to be significantly higher than one-time-off WTP values, suggesting a negative implicit discount rate. Self-selection bias is an important reason for the observed differences. We find that respondents who agree to pay annually differ significantly from respondents who wish to pay a lump-sum in terms of their underlying preferences and motivations towards migratory bird protection.