Willingness to Pay to Reduce Mortality Risks: Evidence from a Three-Country Contingent Valuation Study

Valuing a change in the risk of death is a key input into the calculation of the benefits of environmental policies that save lives. Typically such risks are monetized using the Value of a Statistical Life (VSL). Since the majority of the lives saved by environmental policies are those of older persons, there has been much recent debate about whether the VSL should be lower for the elderly to reflect their fewer remaining life years. We conducted a contingent valuation survey in the UK, Italy and France designed to answer this question. The survey was administered in these three countries following a standardized protocol. Our results suggest that the VSL is €1.022 million or €2.264 million, depending on whether we use median or mean WTP. The VSL is not significantly lower for older persons, but is higher for persons who have been admitted to a hospital or emergency room for cardiovascular and respiratory problems. Income is positively and significantly associated with WTP. The income elasticities of the WTP increase gradually with income levels and are between 0.15 and 0.5 for current income levels in EU countries. We use the responses to the WTP questions to estimate the value of an extension in remaining life expectancy. The value of a loss of one year’s life expectancy is €54,000 or €163,000.     

Construct Validity of Dichotomous and Polychotomous Choice Contingent Valuation Questions

In this note we conduct construct validity tests for dichotomous choice (DC) and polychotomous choice (PC) contingent valuation questions. Contrary to previous results, we find that DC and PC estimates of willingness to pay are theoretically valid, convergent valid, and similar in terms of statistical precision. Similar to previous results, PC respondents are less sensitive to information than DC respondents. We conclude that DC and PC valuation questions are construct valid for this study. Sequential PC valuation questions could be used in studies where obtaining information about the certainty or intensity of respondent preferences would be useful.     

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.     

Contingent valuation of inhaled insulin: a Canadian perspective

Summary

The objective of this study was to assess the preference and willingness-to-pay (WTP) for inhaled insulin from a random sample of general public perspective in Ontario, Canada. This was carried out using a mail survey using the contingent valuation method. Significantly more respondents preferred inhaled insulin (n=114) over subcutaneous insulin (n=6; p<0.001). The mean monthly WTP for inhaled insulin was CAN$68.59 ± 44.65 (95% confidence interval CAN$58.87–78.07), significantly more than the average subcutaneous insulin cost in Ontario of CAN$50. The WTP for inhaled insulin in the diabetic subgroup was CAN$98.52 ± 48.57, which is significantly higher than that of the general public (p<0.001). Multiple regression analysis showed a strong association between respondents’ income and diagnosis of diabetes and their WTP for inhaled insulin (p<0.001). Major influencing factors were convenience and household budget. The results of this study suggest that the general public in Ontario prefer inhaled insulin and are willing to pay significantly more per month than the current cost of subcutaneous insulin.     

Repeated Dichotomous Choice Formats for Elicitation of Willingness to Pay: Simultaneous Estimation and Anchoring Effect

Repeated dichotomous choice contingent valuation data are generated from responses to a succession of binary questions regarding alternative prices for an environmental good. In this paper we propose a simultaneous equation model that allows for endogeneity and error correlation across the responses at each stage of the bidding process. The model allows us to study the evolution of anchoring effects after the second dichotomous choice question. Estimation involves the Bayesian techniques of Gibbs sampling and data augmentation, and the application focuses on the preservation value of a natural area. The results for a data set involving up to four successive dichotomous choice questions show that restricted multiple-bounded models are rejected by the data with the general model. In addition, willingness to pay tends to stabilize after the second stage in the elicitation process for the general unrestricted model. When taking anchoring effects into consideration, it is revealed that individuals’ responses in the latter stages are influenced by the sequence of bid prices offered in earlier questions. Nevertheless, they do not have a significant effect on welfare estimates.      

Addressing Heterogeneous Preferences Using Parametric Extended Spike Models

Some public programs simultaneously provide a mix of non-rejectable public goods and public bads. Consequently, some individuals would pay for the program, while others might instead need to becompensated. In this paper we estimate twoparametric extended spike models that accountfor positive and negative preferences as wellas indifference for the public good. Weillustrate the models using data on valuationof prescribed burning of underbrush in forests,which reduces the risk of catastrophicwildfires but also produces smoke emissions(the public bad). We compare the two empiricalapproaches to estimate willingness to pay (WTP)for the program and contrast these results withthose obtained from modeling specificationsthat only account for non-negative preferences.Substantial differences in public net benefitswere found between the most flexible parametricextended spike model and the simple spike modelwhere negative responses were coded as zero anda standard binary logit of only positivebidders. The results from the extended spikemodels demonstrated that accounting forindifference and negative values towards thepublic good resulted in substantially lowerwillingness to pay estimates.     

南京市公众对长江水质改善的支付意愿及支付方式的调查

本文以南京市为例．利用支付卡式的条件价值评估（OVM）技术．通过发放调查问卷及访谈的形式对公众改善长江水质的支付意愿进行了深入研究。结果表明：（1）南京市居民对长江水质恢复的户均年支付意愿为100．66元．76．5％的受访者的支付意愿大于零，8．4％的受访问者虽有支付意愿但限于低经济收入原因支付意愿为零．15.1％的受访者拒绝支付；（2）影响居民支付意愿的主要因素包括家庭收入、环境意识及文化程度；（3）南京市居民偏爱的支付方式依次为捐款、交税、存取基金方式及提高水价．水价上涨并不是面向公众筹集长江水质改善资金的唯一有效方式。根据调查结果，本文认为增加收入，提高水环境保护意识．引入“谁收益、谁支付”观点是提高居民支付意愿的有效途径。     

Multivariate Mixed Models for Open-Ended Contingent Valuation Data: Willingness To Pay For Conservation of Monk Seals

Although dichotomous choice (DC) contingent valuation (CV) has been recommended by the US NOAA 'blue-ribbon' panel for large-scale contingent valuation studies, useful information can still be obtained from smaller, open-ended (OE) studies, often undertaken as a precursor to a DC survey. The CV study considered here was carried out in Greece and looked at willingness-to-pay (WTP) for protecting the Mediterranean monk seal (Monachus-monachus) in the Aegean area. This is the most endangered seal in the world, and the application of the CV methodology was the first such application in Greece. The OE data consist of two responses: first, a binary response detailing whether or not respondents were in principle prepared to pay for the protection of this seal; secondly, those respondents who answered 'yes' to the first question were then asked to state their maximum WTP for such protection. A multivariate binomial – log-normal mixture model is used to develop a bid function including explanatory variables such as income, sex, age and education. Such a modelling approach provides an alternative to more commonplace tobit estimation. However, the model is extended to include further information which was collected on:(a) an increased WTP amount given in response to information that the initial WTP amount may not be enough to prevent the extinction of the seal;(b) respondents were asked to divide their final WTP amount between use, option and existence values, the latter requiring a multivariate model with four binary and four continuous responses per individual in the same model.The discussion focuses on the methodological issues raised with some comment on the substantive interpretation of results.     

Bid Design Effects in Multiple Bounded Discrete Choice Contingent Valuation

A potential concern in multiple bounded discrete choice contingent valuation surveys – where the respondent is asked to express voting certainty, rather than a simple yes or no, on a large number of payment amounts (bids) – is whether responses are influenced by the particular position of bids in the bid-voting panel rather than solely on the respondents willingness to pay (WTP). For instance, respondents may systematically state they would pay the first few bid amounts and not pay all subsequent bids – regardless of the actual dollar values. Such systematic bid design effects would suggest that this method does not provide a valid measure of WTP. Using a split-sample survey, we compare responses to three different bid arrays that have an identical minimum bid, maximum bid, and number of bids. Using nonparametric estimation techniques, we find that estimated WTP distributions and corresponding welfare measures are not statistically different across survey samples.     

The Economic Value of Air-Pollution-Related Health Risks in China: A Contingent Valuation Study

The economic value of preventing adverse health effects related to air pollution is estimated using contingent valuation in three diverse locations in China. Values are estimated for three health endpoints: cold, chronic bronchitis, and fatality. Alternative statistical models are tested to study their impact on estimated willingness to pay (WTP) and on the relationship between WTP and respondent characteristics. Using the official exchange rate, the sample-average median WTP to prevent an episode of cold ranges between US$3 and US$6, the WTP to prevent a statistical case of chronic bronchitis ranges between US$500 and US$1,000, and the value per statistical life ranges between US$4,000 and US$17,000. Estimated mean values are between two and thirteen times larger. Our estimates are between about 10 and 1,000 times smaller than estimates for the US and Taiwan using official exchange rates. Indoor air quality, measured for a subset of respondents, shows no consistent relationship with WTP.     

Willingness to pay for environmental goods in Norway: A contingent valuation study with real payment

The study seeks to determine the maximum willingness to pay (MWTP) among a random sample of Norwegians, for membership in the largest environmentalist association in Norway, Norges Naturvernforbund (NNV). The study includes three stages: (1) a contingent valuation study, testing hypothetical MWTP; (2) those whose stated MWTP is at or above the current membership fee are then asked to pay this fee; (3) those individuals who do not pay in stage 2 are interviewed, and asked to consider revising their MWTP statement. The study is seemingly the first of its kind in comparing hypothetical and actual MWTP by typing valuation of a public good (the environment) to the value of a private good (membership of the NNV). The results show a rather poor correspondence between hypothetical and actual MWTP, since only 6 out of 64 who stated that they were willing to pay the membership fee in stage 1, actually paid this voluntarily in stage 2. Possible reasons for this discrepancy are discussed, on the basis of data from the telephone interview in stage 3, and on information gathered in stage 1. The data indicate that a substantial part of this discrepancy is due to MWTP being overstated in stage 1, but that other reasons also are important.     

A Bayesian Approach to Double Bounded Contingent Valuation

In this paper we propose a Bayesian approach to model double bounded contingent valuation data. The double bounded elicitation method is interpreted as a two tier iterated process in which the subject is allowed to have a second thought about his/her valuation for the environmental good. Prior information is modelled from the answers to the first dichotomous choice question. The model is Quasi-Bayesian (Q-B) in that the prior distribution refers to mean willingness to pay while the likelihood function refers to the proportions of a multinomial distribution. This model is applied to empirical data from a contingent valuation survey involving the valuation expressed by European tourists for access to natural areas in the Canary Islands. Results show that point estimate of consumer surplus computed with the Q-B model does not differ substantially from single bounded model estimation. In addition, double bounded seems to be quite robust to the choice of the prior model of willingness to pay responses. Comparison with open ended suggests that the Q-B model might be useful to control for strategic response and starting point biases.     

Willingness to Pay for Car Safety: Evidence from Sweden

This study estimates a marginal willingness to pay (WTP) function for a road-mortality risk reduction. Observed marginal WTP from the Swedish car market is used and found to be positively correlated with the baseline risk of the cars. No statistically significant relationships between examined owner attributes, e.g. wealth and background risk, and marginal WTP are found. When comparing the estimated monetary value of a non-marginal risk reduction derived from the integral of the marginal WTP-function with an estimate based on marginal WTP we find, in line with expectations, that the difference between the estimates is negligible for smaller risk reductions and small, 4–10%, also for relatively large risk reductions.      

Modelling the Non-market Environmental Costs and Benefits of Biodiversity Projects Using Contingent Valuation Data

CV studies rarely ask willingness to accept (WTA)questions, yet there are a range of environmentalprojects where there are likely to be potential losersas well as gainers. This paper presents evidence fromsix biodiversity projects that the inclusion ofcontingent compensation payments from thoserespondents who preferred the status quo cansubstantially reduce net project benefits, even whenthe proportion of losers is relatively small. Astatistical model for estimating the mean welfaremeasure from dichotomous choice data which allows forboth positive WTP, zero WTP, and WTA is described. Asmany environmental projects are likely to create bothgainers and losers, we recommend that CV analysts giveserious consideration to the collection and analysisof WTA data otherwise they risk generating biasedestimates of project benefits.     

游客对旅游地教育服务的支付意愿研究

为有计划性、引导性的倡导使用者付费的理念,建立公开透明、科学合理的定价机制,运用条件价值评估法(CVM)对全国12个省12个旅游景区的中国游客进行了实地抽样调查,分析游客对教育服务项目的支付意愿。基于2 800份有效问卷数据,获得了受访者支付意愿的分布形态和规律,构建了游客支付意愿与其影响因素之间关系的模型。结果显示:49.40%的游客愿意支付教育服务费用,平均支付额度为28.6元;游客的年龄、婚姻状态、学历、职业、收入与其教育服务支付意愿之间存在显著性关系,旅游地游客教育水平也直接影响游客的支付意愿,而性别与其支付意愿没有显著的差异。同时,游客的年龄、学历、职业、收入对支付方式的影响较大,64.1%的游客想通过门票支付,27.5%的游客想通过小费支付。     

Minimising Payment Vehicle Bias in Contingent Valuation Studies

The payment vehicle is a crucial element inapplications of the contingent valuation methodbecause it provides the context for payment. However,in many countries a relative unfamiliarity with theuse of tax levies and referenda can affect theplausibility of payment vehicles and lead to paymentvehicle bias. The most commonly used approach fordetermining whether payment bias exists is to usetests of convergent validity. It is demonstrated thatsimple tests of convergent validity can be ineffectivein diagnosing the existence of payment vehicle bias.Payment vehicle bias is found to occur because ofdifferences in the coverage of payment vehicles anddoubts about payment being one-off. When respondentsare found to be protesting against a particularpayment vehicle, the current state of the art approachis to delete them from the sample. In this paper analternative approach that relies on the recoding ofprotest responses is proposed.     

Despairing Over Disparities: Explaining the Difference Between Willingness to Pay and Willingness to Accept

This paper examines the three major explanations for the disparity between willingness-to-pay (WTP) and willingness-to-accept (WTA) observed in contingent value surveys and laboratory experiments: a belief that the results must be biased in some fashion, Hanemann's (1991) substitutes hypothesis, and the loss aversion model proposed by Tversky and Kahneman (1991). Starting from the assumption that individuals make utility maximizing choices, we develop structural equations that yield parametric tests of the hypotheses within a single, non-experimental framework. The approach is flexible enough to incorporate a variety of functional form and distributional assumptions and can be applied to either data from either open-ended bids or dichotomous choice questions. The usefulness of the approach is demonstrated using data from a survey that asked both WTP and WTA questions. The results provide weak support for loss aversion.     

The impact of behavioural risk-reduction interventions on willingness to pay to avoid sexually transmitted infections: a stated preference study of justice-involved youth

Risky health behaviours, such as smoking, drinking and risky sex, are substantial contributors to the U.S. morbidity rates and healthcare costs. While economic models typically regard preferences as stable, a growing literature suggests that information, including how it interacts with intentions and attitudes, plays an important role in unhealthy behaviours. Relatedly, a large health literature demonstrates that theory-based behavioural interventions can successfully change risky behaviour. This study uses the contingent valuation (CV) survey method to investigate the impact of behavioural interventions on a novel outcome measure: the willingness to pay (WTP) to avoid the consequences associated with risky behaviour. Using novel pre- and post-intervention data from Project MARS (Motivating Adolescents to Reduce Sexual Risk), this study estimates the impact of the intervention on elicited WTP to avoid sexually transmitted infections (STIs). It is found that after the intervention, participants’ elicited WTP to avoid STIs were significantly higher, and more sensitive to differences in infection severity. These results suggest that the intervention may affect risky sexual behaviour by changing the perceived value of avoiding the consequences of risky sexual behaviour. Additionally, these findings contribute to an ongoing debate regarding the construct validity of CV studies in health economics.     

On the Asymmetry of the Vagueness Band in Willingness to Pay Answers

The NOAA panel for Contingent Valuation opened up the question of the possibility of using trichotomous choice discrete formats in CV studies. In this paper we show how the trichotomous choice format can be used for testing the successfulness of the project definition in the questionnaire. We shall define the vagueness band around the true outcome of the project to be valued and we allow it to be asymmetric. It is shown how this asymmetry can be modelled and estimated. We also show how these new models are generalisations of ordinary ordered probit/logit models.