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.     

Theoretical incentive properties of contingent valuation questions: Do they matter in the field?

Green et al. (1998) [Green, D., Jacowitz, K.E., Kahneman, D., McFadden, D., 1998. Referendum contigent valuation, anchoring, and willingness to pay for public goods. Resource and Energy Economics 20 (2), 85−116] show theoretically that stated preference questions about public services can be framed in such ways that if the subjects accept the frame the payoff­maximizing behavior will be to answer truthfully. One key element of such a theoretically incentive­compatible framing is that the (hypothetical) decision rule specified in the survey instrument is understood to be a majority rule rather than the efficiency rule typically used in cost­benefit analysis. We conducted field experiments in Germany and Switzerland to test if a referendum framing as suggested by Green et al. is effective in reducing strategic misrepresentation in a contingent valuation setting. We did not find the expected effects of the framing treatments on stated willingness to pay or on individuals' (stated) beliefs about the social choice context. The results do not support hopes that a theoretically incentive compatible framing could be purposefully used to invoke the specific beliefs about the linkage between responses and policy implementation that would make stated preference questions incentive compatible.     

Discrete Choice Experiments in Developing Countries: Willingness to Pay Versus Willingness to Work

A concern when conducting stated preference valuation studies in rural developing or very low income contexts is the use of monetary willingness to pay (WTP) estimates. In circumstances where cash incomes are extremely low, a significant proportion of the population are not engaged in waged labour and the exchange of goods or services is augmented through barter or work exchange, the role of money is likely to be different from that within an urban developed setting. As such, ability to pay using money may be impaired and downwardly biased when compared with other mediums of exchange. In recognition of this several studies have used hypothetical labour contributions as payment vehicles and a common finding is that households are more often willing to contribute labour than they are money. In this paper we present the results of a split sample DCE using money and labour contributions as payment vehicles for improved drinking water quality in Kandal Province, Cambodia. We find little differences between the payment vehicles in terms of attribute non-attendance, marginal utilities of attributes or derived welfare values. We argue that this provides support for the use of WTP in rural developing areas where there are functioning labour markets.     

Indices of biotic integrity in stated preference valuation of aquatic ecosystem services

Stated preference surveys often give minimal attention to distinctions between intermediate and final ecosystem services, leading to the potential for welfare estimates that overlook, misrepresent or double count associated values. This paper illustrates potential mechanisms through which multimetric indexes of the type developed in the ecological literature, here an index of biotic integrity, can be used within stated preference survey scenarios to both improve the validity of survey responses and provide otherwise unavailable information on willingness to pay for intermediate and final ecosystem services. We illustrate the approach using a choice experiment application to the restoration of migratory fish in a Rhode Island watershed. Where assumptions of the model hold, results can allow transparent disentanglement and estimation of marginal values for both intermediate and final ecosystem services.     

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.     

Willingness to pay for electric vehicles and their attributes

This article presents a stated preference study of electric vehicle choice using data from a national survey. We used a choice experiment wherein 3029 respondents were asked to choose between their preferred gasoline vehicle and two electric versions of that preferred vehicle. We estimated a latent class random utility model and used the results to estimate the willingness to pay for five electric vehicle attributes: driving range, charging time, fuel cost saving, pollution reduction, and performance. Driving range, fuel cost savings, and charging time led in importance to respondents. Individuals were willing to pay (wtp) from $35 to $75 for a mile of added driving range, with incremental wtp per mile decreasing at higher distances. They were willing to pay from $425 to $3250 per hour reduction in charging time (for a 50 mile charge). Respondents capitalized about 5 years of fuel saving into the purchase price of an electric vehicle. We simulated our model over a range of electric vehicle configurations and found that people with the highest values for electric vehicles were willing to pay a premium above their wtp for a gasoline vehicle that ranged from $6000 to $16,000 for electric vehicles with the most desirable attributes. At the same time, our results suggest that battery cost must drop significantly before electric vehicles will find a mass market without subsidy.     

A comparison of responses to single and repeated discrete choice questions

According to neoclassical economic theory, a stated preference elicitation format comprising a single binary choice between the status quo and one alternative is incentive compatible under certain conditions. Formats typically used in choice experiments comprising a sequence of discrete choice questions do not hold this property. In this paper, the effect on stated preferences of expanding the number of binary choice tasks per respondent from one to four is tested using a split sample treatment in an attribute-based survey relating to the undergrounding of overhead low-voltage electricity and telecommunications wires. We find evidence to suggest that presenting multiple choice tasks per respondent decreases estimates of expected willingness to pay. Preferences stated in the first of a sequence of choice tasks are not significantly different from those stated in the incentive compatible single binary choice task, but, in subsequent choice tasks, responses are influenced by cost levels observed in past questions. Three behavioural explanations can be advanced – weak strategic misrepresentation, reference point revision, and asymmetric value learning. The evidence is contrary to the standard assumption of truthful response with stable preferences.     

What to Value and How? Ecological Indicator Choices in Stated Preference Valuation

The ecological literature accepts that many policy outcomes cannot be observed directly and must be characterized using indicators. Multiple indicators can often be used to communicate similar ecological outcomes. Previous studies using alternative indicators in stated preference surveys suggest that welfare estimates may be indicator-dependent, casting doubt on whether welfare estimates are sufficiently reliable for cost benefit analysis. We suggest that the reason for such indicator dependence may be that indicators used in these prior studies represented different outcomes valued by respondents. This possibility underscores the need for greater attention to selection of indicators and their properties within stated preference survey design. This paper develops a model introducing the concept of outcome equivalent indicators, defined as indicators that provide alternative representations of identical underlying outcomes. To assess empirically whether welfare estimates are indeed robust to indicator choice when alternative indicators are expected to be outcome equivalent, we analyze data from a choice experiment estimating willingness to pay for migratory fish restoration in Rhode Island, USA. Results demonstrate that welfare estimates are robust to the use of alternative ecological indicators within stated preference scenarios.     

Dealing with preference uncertainty in contingent willingness to pay for a nature protection program: A new approach

In this paper, we propose an alternative preference uncertainty measurement approach where respondents have the option to indicate their willingness to pay (WTP) for a nature protection program either as exact values or intervals from a payment card, depending on whether they are uncertain about their valuation. On the basis of their responses, we then estimate their degree of uncertainty. New within this study is that the respondent's degree of uncertainty is “revealed”, while it is “stated” in those using existing measurement methods. Three statistical models are used to explore the sources of respondent uncertainty. We also present a simple way of calculating the uncertainty adjusted mean WTP, and compare this to the one obtained from an interval regression. Our findings in terms of determinants of preference uncertainty are broadly consistent with a priori expectations. In addition, the uncertainty adjusted mean WTP is quite similar to the one derived from an interval regression. We conclude that our method is promising in accounting for preference uncertainty in WTP answers at little cost to interviewees in terms of time and cognitive effort, on the one hand, and without researcher assumptions regarding the interpretation of degrees of uncertainty reported by respondents, on the other.     

Mixed logit estimation of willingness to pay distributions: a comparison of models in preference and WTP space using data from a health-related choice experiment

Different approaches to modelling the distribution of WTP are compared using stated preference data on Tanzanian Clinical Officers’ job choices and mixed logit models. The standard approach of specifying the distributions of the coefficients and deriving WTP as the ratio of two coefficients (estimation in preference space) is compared to specifying the distributions for WTP directly at the estimation stage (estimation in WTP space). The models in preference space fit the data better than the corresponding models in WTP space although the difference between the best fitting models in the two estimation regimes is minimal. Moreover, the willingness to pay estimates derived from the preference space models turn out to be very high for many of the job attributes. The results suggest that sensitivity testing using a variety of model specifications, including estimation in WTP space, is recommended when using mixed logit models to estimate willingness to pay distributions.     

Heterogeneous Preferences for Community Recycling Programs

This paper examines household preferences for community recycling programs, which have both public and private good dimensions. The data come from a survey conducted in Seattle (WA) which elicited stated preference-contingent ratings for different recycling programs relative to status quo, with experimental variation in the overall community recycling rate achieved and expected household cost. The recycling rate is interpreted as capturing the public benefits of recycling programs and constitutes the most common measure used by policy agencies for setting waste management objectives and evaluating policy initiatives. The analysis begins with fixed parameter models that explore different ways of handling rating data and mixed logit estimations that capture household preference heterogeneity both within and across different recycling programs. This analysis yields unique estimates of willingness to pay for an increase in the community recycling rate. Predicted individual-specific utility parameters are then regressed on household background information to explicitly examine the nature of preference heterogeneity. Overall, this paper generates interpretable policy-relevant insights into the public and private good dimensions of community recycling programs.     

Should all Choices Count? Using the Cut-Offs Approach to Edit Responses in a Choice Experiment

Should we give equal weight to all responses in a choice experiment? Previous Choice Modelling papers have considered the issue of the internal consistency of choices—such as the extent to which strictly-dominated options are chosen. In this paper, a different focus is employed, namely the extent to which people choose options which violate their stated upper or lower limits for the acceptable levels for individual attributes. Since hypothetical over-statement of WTP has been a focus in stated preference studies, we concentrate on violations of stated upper limits of WTP, and explore the effects of “editing” such choices using a variable censoring rule and alternative approaches to re-classifying choices. The empirical case study is a choice experiment on eco-tourists in Rwanda. Our main conclusion is that the suggested approach offers a useful way of imposing consistency on choices, and that editing choices in this manner has an appreciable impact on estimated willingness to pay. However, issues remain with regard to explaining why people apparently violate their stated maximum willingness to pay.     

Deliberative monetary valuation (DMV): Issues in combining economic and political processes to value environmental change

This paper explores and contrasts the different social processes of valuation now appearing as economic means of valuing the environment. Monetary valuation via stated preference approaches has been criticised for assuming well formed and informed preferences and excluding a range of sustainability concerns such as rights, fairness and equity. Deliberative monetary valuation (DMV) in small groups is a novel hybrid of economic and political approaches which raises the prospect of a transformative and moralising experience. Critics of standard contingent valuation approaches have advocated this as offering a way forward. However there has been a lack of clarity as to the means of obtaining values, the expected outcomes and their role. Moving to group settings of deliberation raises concepts of social willingness to pay and accept which are distinct from an aggregate of individual value, although this does not seem to have been widely recognised. A new classification of values is presented appropriate to the literature trying to merge economic and political processes. Values associated with the individual may be exchange values, charitable contributions or fair prices, while social values can be speculative, expressive or arbitrated. The use of DMV is shown to result in different values due to variations in the institutional setting and process of valuation.     

Temporal stability of preferences and willingness to pay for natural areas in choice experiments: A test–retest

The main objective of this paper is to test the temporal stability of stated preferences and willingness to pay (WTP) values from a Choice Experiment (CE) in a test–retest. The same group of participants was asked the same choice tasks in an internet-based CE, conducted twice with a time interval of one year without interviewer interference. We examine choice consistency at individual choice task level and transferability of the underlying indirect utility function and associated WTP values. The results show that choices are consistent in 57 percent of the choice occasions. Comparison of the choice models over time shows that the estimated preference and scale parameters are significantly different, suggesting that choice behaviour changed between the two surveys. Differences between marginal WTP estimates for individual choice attributes are statistically significant only at the 10 percent level. However, we show that this can result in significantly different WTP values for policy scenarios. The instability of estimated mean WTP values for different policy scenarios asks for caution when including WTP values in cost-benefit analysis.     

Choice Consistency and Preference Stability in Test-Retests of Discrete Choice Experiment and Open-Ended Willingness to Pay Elicitation Formats

This study tests the temporal stability of preferences, choices and willingness to pay (WTP) values using both discrete choice experiment (DCE) and open-ended (OE) WTP elicitation formats. The same sample is surveyed three times over the course of two years using each time the same choice sets. Choice consistency is positively correlated with choice certainty and choice complexity. The impact of choice complexity fades away in time, most likely as a result of learning and preference refinement. Although the OE WTP values remain stable over a time period of 2 years as in previous stated preference studies, DCE based WTP measures differ significantly, suggesting their use in benefits transfer may be limited.     

Sad or Happy? The Effects of Emotions on Stated Preferences for Environmental Goods

A substantial literature in behavioural science and psychology shows that emotions affect human choices and values. This paper investigates whether such emotional impacts are also present in stated choice experiments for environmental goods. If this were so, it would introduce an additional element of context dependence to the welfare measures derived from such methods, and would be at odds with the rational choice model underlying welfare economics. A laboratory experiment using three different emotion treatments was combined with a stated preference choice experiment concerned with changes in coastal water quality and fish populations in New Zealand. No statistically significant effects of changes in emotional state on estimated preference parameters, willingness to pay or the randomness of choices were found. The paper concludes by questioning, why such a contrast exists with empirical findings in behavioural science.     

The Effect of Risk Context on the Value of a Statistical Life: a Bayesian Meta-model

This paper presents the first value of statistical life (VSL) meta-analysis that empirically estimates correction factors for ‘out of context’ benefits transfer (BT) purposes. In the field of mortality risk reductions elicited willingness to pay values in one risk context, say road safety, are frequently applied in other risk contexts like air pollution. However, differences in risk perception and the population at risk across contexts are likely to result in diverging VSL estimates. In a meta-analysis of 26 international stated preference studies, a Bayesian model is estimated regressing contingent values for mortality risk reductions, originating from three different risk contexts, on the characteristics of the risk reduction itself and additional variables characterizing the underlying studies. A willingness to pay (WTP) premium for mortality risk reductions in the air pollution and general mortality risk context relative to improving road safety is observed. Evaluated at the mean, road safety VSL estimates should be multiplied by a factor 1.8 before being applicable in the air pollution context. Moreover, in an illustrative BT exercise we find limited overlap in the set of context specific predictive VSL distributions. Consequently, ‘out of context’ BT results in a substantial over- or underestimation of the VSL.     

茶农生物农药属性偏好及支付意愿研究——基于选择实验的实证分析

利用选择实验方法实证分析了茶农生物农药属性偏好和支付意愿。结果表明:(1)茶农偏好"缩短安全间隔期""不提前使用"和"不产生抗药性"的农药属性,但在"缩短安全间隔期"和"针对防治"上存在偏好异质性;(2)茶农愿为优化3类属性多支付16.974、22.250和11.272元/亩/年;(3)种植面积小、受教育年限长、化学农药危害认知程度高的茶农倾向于选择生物农药;(4)生物农药实际支付高于各属性加总的意愿支付,应关注生物农药外部性。     

The willingness to pay for mortality risk reductions in Mongolia

This paper reports results from a stated preference survey designed to estimate the willingness to pay for mortality risk reductions in Ulaanbaatar, Mongolia. The survey includes both contemporaneous and latent risk reductions of a magnitude typically achievable through clean air policy. The study is one of a series of national studies designed to provide comparable estimates around the world. One goal of this series is to build a more solid bridge for benefits transfer between developed and developing countries. The survey was conducted in winter 2010. Estimates of willingness to pay passed external and internal scope tests. Study results imply a value of statistical life of approximately $500,000 (based on a purchasing power parity exchange rate) for a contemporaneous 5-in-10,000 annual risk reduction.     

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.